Impaired early left ventricular relaxation in coronary artery disease: effects of intracornary nifedipine

Left ventricular function during transluminal angioplasty: a haemodynamic and angiographic study

The response of left ventricular function, was studied in a series of patients undergoing percutaneous transluminal coronary angioplasty (PTCA). From 4 to 6 balloon inflations procedures per patient were performed with an average duration per occlusion of 51 +/- 12 sec (mean +/- SD), total occlusion time 252 +/- 140 sec. Analysis of left ventricular (LV) haemodynamics showed that the relaxation parameters peak negative rate of change in pressure and the early time constant of relaxation responded earliest to acute coronary occlusion while other parameters such as peak pressure, LV end-diastolic pressure, and peak positive rate of change of pressure responded more gradually and suggested a progressive depression in myocardial mechanics during the entire procedure. LV angiogram available in 14 patients indicate an early onset of asynchronous relaxation concurrent with the early response in peak -dP/dt and the time constant of early relaxation. All haemodynamic parameters fully recovered within minutes after the end of PTCA. The results of this study indicate no permanent dysfunction to global or regional myocardial mechanics, after PTCA with 4 to 6 coronary occlusions each lasting 40 to 60 seconds.

Possible contribution of the sarcoplasmic reticulum Ca(2+) pump function to electrical and mechanical alternans

We investigated the role of the sarcoplasmic reticulum's (SR) Ca(2+) pump function of the in the mechanism of alternans. We recorded the surface ECG, monophasic action potential (MAP) and left ventricular pressure (LVP) in the canine beating heart. Alternans was induced with an abrupt shortening of the cycle length from 1000 to 350 ms. After the control studies, we administered propranolol or isoproterenol. In the presence of propranolol, we administered milrinone or 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). In the presence of isoproterenol, we administered thapsigargin. Isoproterenol and milrinone attenuated both the electrical and mechanical alternans. Thapsigargin, a specific SR Ca(2+) pump inhibitor, and propranolol magnified both types of alternans. DIDS, a Ca(2+)-activated Cl(-) current (I(Cl(Ca))) inhibitor, attenuated the MAP alternans without an affect on the LVP alternans. Thus, the delayed intracellular Ca(2+) cycling caused by the impaired SR Ca(2+) pump function might produce electrical and mechanical alternans. beta-adrenergic stimulation eliminated these alternans. The I(Cl(Ca)) contributed to the appearance of the electrical alternans.

Controlled hypotension in children: a critical review of available agents

Due to the potential for the transmission of infectious diseases with the homologous transfusion of blood products, there has been an increased interest in measures to limit intraoperative blood loss and avoid the need for homologous transfusion during high-risk surgical procedures including spinal surgery. Controlled hypotension (also referred to as deliberate or induced hypotension), defined as a reduction of systolic blood pressure to 80 to 90 mm Hg, a reduction of mean arterial pressure (MAP) to 50 to 65 mm Hg or a 30% reduction of baseline MAP, is one technique that has been used to limit intraoperative blood loss. In the adult population, several agents have been used alone or in combination for controlled hypotension including the inhalational anesthetic agents, direct-acting vasodilators such as nitroglycerin (glyceryl trinitrate) and nitroprusside, beta-adrenoceptor antagonists, and calcium channel antagonists. Despite clinical studies that have clearly demonstrated a reduction in blood loss with controlled hypotension when compared with the normotensive state and despite potential theoretical issues with each agent, there are no definitive studies demonstrating the preferred pharmacologic agent. When considering the pediatric-aged patient, studies have reported the use of the inhalational agent sevoflurane, the alpha(2)-adrenoceptor agonist dexmedetomidine as well as various vasodilators including sodium nitroprusside, nitroglycerin, fenoldopam, and alprostadil for controlled hypotension. Sevoflurane offers the advantages of easy dosage titration, no need for an additional intravenous infusion as well as providing anesthesia in addition to controlled hypotension. Disadvantages include a slightly higher cost than some of the intravenous agents and the inability to monitor evoked potentials with high sevoflurane concentrations. Whereas sodium nitroprusside, nicardipine and fenoldopam all provide the desired level of hypotension in pediatric-aged patients, nitroglycerin was not effective in this age group of patients in one study. When comparing nicardipine and sodium nitroprusside, nicardipine offers the potential advantages of fewer episodes of excessive hypotension, less rebound tachycardia and, in one study, less blood loss. Although fenoldopam has been shown to be effective, cost issues may limit is widespread application for this technique. The pharmacologic profile of dexmedetomidine indicates that this drug has potential in controlled hypotension and clinical data are needed to define its role.

Post-endsystolic active shortening in the non-ischemic region impairs left ventricular pressure fall in acute ischemic heart

To investigate the relation between the impairment of isovolumic relaxation and the regional wall motion in acute ischemia, the left ventricular pressure fall and regional myocardial motion were examined in the relaxation phase in dogs during both acute coronary artery occlusion (n = 12) and a regional coronary flow reduction (n = 6). Fifteen to 40 seconds after complete coronary artery occlusion or in the stable state after a regional coronary flow reduction by 70 to 90% of the control state, a shortening of the non-ischemic region at the early isovolumic relaxation phase (the post-endsystolic shortening) appeared, combined with lengthening of the ischemic region. In these situations, the logarithmic plots of the left ventricular pressure fall was composed of two components (time constant of early part [Ta] and at latter part [Tb]). Ta was greater than Tb (64.3 +/- 13.8 milliseconds vs. 36.6 +/- 10.4 milliseconds at 15 seconds after coronary occlusion, p < 0.01; 67.6 +/- 22.9 milliseconds vs. 45.1 +/- 17.5 milliseconds at flow reduction, p < 0.01) and the time constant at control (p < 0.01). These findings suggested that post-endsystolic shortening in the non-ischemic region played a role in a the non-uniformity of the left ventricular contraction and contributed to the impairment of the left ventricular pressure fall in acute regional ischemia, especially in early isovolumic relaxation.

Decreased expression of myocardial eNOS and caveolin in dogs with hypertrophic cardiomyopathy

Because nitric oxide (NO) regulates cardiac and vessel contraction, we compared the expression and activity of the endothelial NO synthase (eNOS) and caveolin, which tonically inhibits eNOS in normal and hypertrophic cardiomyopathic hearts. NOS activity (L-[(3)H]citrulline formation), eNOS immunostaining, and caveolin abundance were measured in heart tissue of 23 mongrel dogs before and at 3 and 7 wk of perinephritic hypertension (PHT). Hemodynamic parameters in vivo and endothelial NO-dependent relaxation of macro- and coronary microvessels in vitro were assessed in the same animals. eNOS immunostaining and total calcium-dependent NOS activity decreased at 7 wk in all four heart cavities (in left ventricle, from 17.0 +/- 1.3 to 0.2 +/- 0.2 fmol. min(-1). mg protein(-1), P < 0.001). Caveolin-1 and -3 also decreased in PHT dog hearts. Accordingly, basal vascular tone was preserved, but maximal endothelial NO-dependent relaxation was impaired in all vessels from 7-wk PHT dogs. The latter had preserved systolic function but impaired diastolic relaxation [relaxation time constant (T(1)), 25.1 +/- 0.9 vs. 22.0 +/- 1 ms in controls; P < 0.05]. Peripheral infusion of the NOS inhibitor N(G)-nitro-L-arginine methyl ester increased mean aortic pressure in both groups and reduced diastolic (T(1), 31.9 +/- 1.4 ms) and systolic function in PHT dogs (DP40, 47.5 +/- 2.5 vs. 59.4 +/- 3.8 s(-1) in control animals). In conclusion, both eNOS and caveolin proteins are decreased in the hypertrophic hearts of PHT dogs. This is associated with altered maximal (but not basal) vascular relaxation and impaired diastolic function. Further degradation of cardiac function after NOS inhibition suggests a critical role of residual NOS activity, probably supported by the concurrent downregulation of caveolin.

Logistic time constant of isometric relaxation force curve of ferret ventricular papillary muscle: reliable index of lusitropism

We have found that a logistic function fits the left ventricular isovolumic relaxation pressure curve in the canine excised, cross-circulated heart more precisely than a monoexponential function. On this basis, we have proposed a logistic time constant (tau(L)) as a better index of ventricular isovolumic lusitropism than the conventional monoexponential time constant (tau(E)). We hypothesize in the present study that this tau(L) would also be a better index of myocardial isometric lusitropism than the conventional tau(E). We tested this hypothesis by analyzing the isometric relaxation force curve of 114 twitches of eight ferret isolated right ventricular papillary muscles. The muscle length was changed between 82 and 100% L(max) and extracellular Ca(2+) concentrations ([Ca(2+)](o)) between 0.2 and 8 mmol/l. We found that the logistic function always fitted the isometric relaxation force curve much more precisely than the monoexponential function at any muscle length and [Ca(2+)](o) level. We also found that tau(L) was independent of the choice of the end of isometric relaxation but tau(E) was considerably dependent on it as in ventricular relaxation. These results validated our present hypothesis. We conclude that tau(L) is a more reliable, though still empirical, index of lusitropism than conventional tau(E) in the myocardium as in the ventricle.

Unsolved problems in diastole

It is now recognized that a sizable portion of patients who exhibit symptoms of congestive heart failure have relatively well-preserved systolic function, but have significantly elevated LV filling pressures. This syndrome, termed "diastolic heart failure," is associated with various conditions such as aging, anatomic abnormalities, hypertension, ischemic disease, tachycardia, and atrial fibrillation. Advances in the proper medical and surgical management of these patients will depend on the continued delineation of the basic physiologic mechanisms that account for normal and pathologic cardiac diastolic function. This goal can only be achieved by the integration of information acquired from basic science investigations conducted in vitro and in vivo, mathematic modeling simulation studies, and prospective, community-based investigations that characterize the incidence, prevalence, and natural history of the disease. In addition, randomized clinical trials will be needed to determine the optimal treatment strategies for this group of patients--strategy choices undoubtably complicated by a disease whose treatment is influenced to a large extent by its origin. The future therapies evaluated in these randomized clinical trials will most likely range from medical therapies that target either the heart directly or the peripheral vascular system, to surgical interventions such as direct myocardial revascularization, to gene therapy. Finally, it is worth mentioning one more unresolved issue that is of general practical concern not only to the physiologist studying diastolic function, but also to the clinician: whether or not it is even feasible to develop a single, sensitive, specific, clinically relevant index of diastolic function that is free from the contaminating influences of rate, contractility, and load. As observed by Glantz 20 years ago, developing indexes with the hope that one might fully delineate the left ventricle's diastolic properties, rather than concentrating on discovering the physiologic significance of such indexes, is probably counterproductive. More recently, in a related article, Slinker implied that an operational definition of any aspect of cardiac function must allow for the measurement of that function over an adequate range of essential variables. Therefore, as previously mentioned, the physiologist studying cardiac function has the daunting task of trying to understand, in a precise way, how the processes and mechanisms of the various phases of the cardiac cycle couple together to produce either a normal or abnormal functioning heart. It seems clear that because of the complex weave of factors that control overall cardiac diastolic function, the derivation of any single index that adequately describes LV diastolic function in vivo may not be possible.

Four-parametric non-linear regression fit of isovolumic relaxation in isolated ejecting rat and guinea pig hearts

Left ventricular isovolumic pressure fall is characterized by the time constant tau obtained by fitting the exponential p(t) = p(infinity) + (p(0)-p(infinity))3exp(-t/tau) to pressure fall. It has been shown that tau, calculated from the first half of pressure fall, differs considerably from that found at late relaxation in normal and pathophysiological conditions. The present study aims at testing for such differences statistically and to quantify tau changes during relaxation. Two improvements of the common regression procedure are introduced for that purpose: the use of the four-parametric regression function, p(t) = p(infinity) + (p(0)-p(infinity))3exp[-t/(tau(0)+b(tau)t)], and an optimal data-dependent split of the isovolumic pressure fall interval. The residual regression errors of the methods are statistically compared in one-hundred isolated working rat and one-hundred guinea pig hearts, additionally including a logistic regression method. Regression error is significantly reduced by introducing that b(tau). b(tau) is negative in most cases, indicating accelerated relaxation during isovolumic pressure fall, but zero and positive b(tau) are occasionally seen. Optimal interval tripartition further improves the regression error in most cases. The statistically proved acceleration of the time constant during isovolumic relaxation justifies factor b(t) as a direct and continuous measure of differences between early and late relaxation. This difference between early and late isovolumic relaxation is probably caused by residually contracted myocardium at the beginning of pressure fall, and is therefore important to describe pathophysiological effects on relaxation phases.

Comparison of ventricular pressure relaxation assessments in human heart failure: quantitative influence on load and drug sensitivity analysis

OBJECTIVES

We contrasted various methods for assessing ventricular pressure decay time constants to test whether sensitivity to slight data instability or disparities between model-assumed and real decay are systematically altered by cardiac failure. We hypothesized that such discrepancies could result in apparent increased relaxation sensitivity to load and drug stimulation.

BACKGROUND

Deviation of relaxation behavior from model-assumed waveforms may be worsened by failure, enhancing instability and apparent load and drug sensitivity of commonly used indexes.

METHODS

Pressure-volume relations were measured in patients with normal (n = 14), hypertrophic (hypertrophic cardiomyopathy [HCM], n = 15) and dilated-myopathic (dilated cardiomyopathy [DCM], n = 37) hearts before and during preload reduction or inotropic stimulation. Relaxation parameters (monoexponential [ME] model assuming zero-T(in) or non-zero-T(D), T(F) asymptote:, hybrid logistic-T(L), linear-T(LR), and pressure halftime-T(1/2)) were contrasted regarding sensitivity to slight data range manipulation and loading or drug changes.

RESULTS

In DCM, T(D) and T(F) prolonged 15% to 25% (p < 0.0001) by deletion of only 1-2 data points, whereas this had minimal effect on controls or HCM. This stemmed from systematic deviation of relaxation from an ME decay in DCM. T(1/2) and T(in) were highly sensitive to pure pressure offsets, whereas T(L) was most stable to both manipulations in all hearts. As a result, T(D) and T(F) appeared to be much more sensitive to systolic load in DCM than T(1/2) or T(L) and disproportionately sensitive to increased cyclic adenosine monophosphate (cAMP).

CONCLUSIONS

Relaxation consistently deviates from an ME decay in DCM resulting in instability and amplified relaxation systolic load or drug dependence of ME-based indexes in failing versus control (or HCM) hearts. The hybrid-logistic method improves quantitative analyses by providing more consistent data fits with all three heart types.

Human SERCA2a levels correlate inversely with age in senescent human myocardium

OBJECTIVES

This study sought to characterize functional impairment after simulated ischemia-reperfusion (I/R) or Ca2+ bolus in senescent human myocardium and to determine if age-related alterations in myocardial concentrations of SERCA2a, phospholamban, or calsequestrin participate in senescent myocardial dysfunction.

BACKGROUND

Candidates for elective cardiac interventions are aging, and an association between age and impairment of relaxation has been reported in experimental animals. Function of the sarcoplasmic reticulum resulting in diastolic dysfunction could be dysregulated at the level of cytosolic Ca2+ uptake by SERCA2a, its inhibitory subunit (phospholamban), or at the level of Ca2+ binding by calsequestrin.

METHODS

Human atrial trabeculae from 17 patients (45-75 years old) were suspended in organ baths, field simulated at 1 Hz, and force development was recorded during I/R (45/120 min). Trabeculae from an additional 12 patients (53-73 years old) were exposed to Ca2+ bolus (2-3 mmol/L bath concentration). Maximum +/- dF/dt and the time constant of force decay (tau) were measured before and after I/R or Ca2+ bolus and related to age. SERCA2a, phospholamban, and calsequestrin from 12 patients (39-77 years old) were assessed by immunoblot.

RESULTS

Functional results indicated that maximum +/-dF/dt and tau were prolonged in senescent (>60 years) human myocardium after I/R (p < 0.05). Calcium bolus increased the maximum +/-dF/dt and decreased tau in younger, but not older patients (p < 0.05). SERCA2a and the ratio of SERCA2a to either phospholamban or calsequestrin were decreased in senescent human myocardium (p < 0.05).

CONCLUSIONS

Senescent human myocardium exhibits decreased myocardial SERCA2a content with age, which may, in part, explain impaired myocardial function after either I/R or Ca2+ exposure.

Different left ventricular relaxation parameters in isolated working rat and guinea pig hearts. Influence of preload, afterload, temperature, and isoprenaline

In isolated ejecting rat and guinea pig hearts, the sensitivity of the time constant tau of left ventricular isovolumic pressure fall, the maximum pressure fall velocity min LVdP/dt, and the relaxation time to different hemodynamic conditions, temperature, and isoprenaline were investigated. Tau was obtained by fitting the isovolumic pressure fall three-parametrically to the exponential p(t) = p infinity + (p0-p infinity) exp (-t/tau) which was found to be superior to semilogarithmic estimation. The influence of different working conditions on the relaxation parameters was tested by a rank correlation test and quantified by calculating standardized regression coefficients. Hemodynamic conditions were altered by changing left ventricular end-diastolic pressure (increasing inflow to the heart) and peak pressure (max LVP, varying aortic outflow resistance), and by atrial pacing (variation of interbeat interval). Lusitropic sensitivity was investigated by changing temperature and by applying isoprenaline. All regression parameters were only moderately sensitive to changes in end-diastolic pressure, max LVP, or heart rate, with the exception of a considerable afterload dependence of min LVdP/dt in rat hearts. This dependence, however, can be overcome to a large extent by dividing min LVdP/dt by mean aortic pressure. Isoprenaline strongly influenced all relaxation parameters, and so did temperature, except for relaxation time in guinea pig hearts. We conclude that tau serves as a reliable relaxation parameter, also in the hearts of small animals with heart rates up to 450 beats/min. In isolated hearts, min LVdP/dt, corrected for afterload dependence, is also suitable as a complementary index of the early relaxation phase.

Dose-related hemodynamic and electrocardiographic effects of the calcium promoter BAY y 5959 in the presence or absence of congestive heart failure

OBJECTIVES

The aim of this study was to assess the cardiovascular effects of BAY y 5959, a calcium promoter modulating myocardial calcium channels, in the presence or absence of congestive heart failure.

BACKGROUND

There is still a clinical need for short-term administration of intravenous positive inotropes. BAY y 5959 was developed as a new approach to increase myocardial performance by selectively enhancing calcium influx in the myocytes.

METHODS

Forty-one patients (21 without and 20 with congestive heart failure) were studied in an open label, dose-ranging study. Hemodynamic variables (including left ventricular [LV] angiography) and plasma samples were obtained at baseline and after 20 min of intravenous infusion of BAY y 5959 at doses ranging from 0.25 to 4.5 microg/kg body weight per min.

RESULTS

In both study groups, BAY y 5959 produced dose-dependent increases in the indexes of inotropic state, without affecting isovolumetric relaxation rate. The magnitude of the response was comparable in patients with or without heart failure (average 38% increase in maximal first derivative of LV pressure [dP/dt max] at plasma levels of 100 microg/liter). BAY y 5959 also induced mild but statistically significant bradycardia and significantly decreased end-systolic volume while producing a leftward shift of the pressure-volume loop. Mean aortic pressure was unaffected at doses up to 3.0 microg/kg per min, and cardiac index improved in patients with heart failure at doses of 2.0 microg/kg per min (+23%, p < 0.05). However, at a dose of 4.5 microg/kg per min, mean aortic pressure and LV systolic wall stress increased, suggesting systemic vasoconstriction. The QT interval was also prolonged significantly at most doses.

CONCLUSIONS

BAY y 5959 exhibits positive inotropic effects in patients with and without heart failure. The optimal response--combining bradycardia, reduced preload and improved cardiac output--appeared to be achieved at a dose of approximately 2.0 microg/kg per min. The impact of QT prolongation with regard to potential antiarrhythmic or proarrhythmic effects is unclear at this time.

Postextrasystolic left ventricular isovolumic pressure decay is not monoexponential

OBJECTIVE

The relationship between the left ventricular (LV) relaxation time constant and early diastolic filling is not fully defined. This study provides additional evidence that LV isovolumic pressure fall in the normal intact heart in response to certain interventions is not adequately described by a model of monoexponential decay and that its relationship to filling is complex.

METHODS AND RESULTS

To gain further insight into the relationship between LV relaxation and early rapid filling we measured LV isovolumic relaxation rate, peak early filling velocity (E), LV volumes, and transmitral pressures at baseline and in the first postextrasystolic beat after a short-coupled extrasystole in 9 anesthetized dogs. Postextrasystolic isovolumic relaxation rate was slowed as measured by 3 commonly used time constants, while E was increased 32%. LV contractility and peak pressure were also increased, while LV end-systolic volume was decreased. LV minimum pressure was deceased, while the early diastolic transmitral pressure gradient was increased. Although all relaxation time constants measured over the entire isovolumic relaxation phase indicated slowed relaxation, direct measurement of isovolumic relaxation time indicated no change in relaxation rate. Calculation of the time constants and direct measurement of isovolumic relaxation time during early isovolumic pressure decay indicated slowed postextrasystolic pressure decay rate compared with baseline, while calculation of time constants and direct measurement of isovolumic relaxation time during late isovolumic relaxation indicated augmented postextrasystolic pressure decay rate versus baseline.

CONCLUSIONS

This non-exponential behavior of LV isovolumic pressure decay in postextrasystolic beats after short-coupled extrasystoles provides further evidence that the relationship that exists between ventricular relaxation and early filling is not simple. The results are interpreted in terms of current theoretical formulations that attribute control of myocardial relaxation to the interaction between inactivation-dependent and load-dependent mechanisms.

Noninvasive Doppler-derived myocardial performance index: correlation with simultaneous measurements of cardiac catheterization measurements

A simple, reproducible, noninvasive Doppler index for the assessment of overall cardiac function has been described previously. The purpose of this study was to correlate the Doppler index with accepted indexes of cardiac catheterization of left ventricular performance. Thirty-four patients with ischemic heart disease or idiopathic dilated cardiomyopathy prospectively underwent a simultaneous cardiac catheterization and Doppler echocardiographic study. Invasive measurements of peak +dP/dt, peak -dP/dt, and tau were obtained from the high-fidelity left ventricular pressures. A Doppler index of myocardial performance was defined as the summation of isovolumetric contraction and relaxation time divided by ejection time. There was a correlation between Doppler measurement of isovolumetric contraction time and peak +dP/dt (r = 0.842; p < 0.0001) and Doppler measurement of isovolumetric relaxation time and peak -dP/dt (r = 0.638; p < 0.001). Left ventricular ejection time correlated with both peak +dP/dt (r = 0.539; p < 0.001) and peak -dP/dt (r = 0.582; p < 0.001). The Doppler index correlated with simultaneously recorded systolic peak +dP/dt (r = 0.821; p < 0.0001) and diastolic peak -dP/dt (r = 0.833; p < 0.001) and tau (r = 0.680; p < 0.0001). This study documents that a simple, easily recordable, noninvasive Doppler index of myocardial performance correlates with invasive measurement of left ventricular systolic and diastolic function and appears to be a promising noninvasive measurement of overall cardiac function.

Early diastolic regional function of the hypertrophied left ventricle

We analyzed cardiac catheterization data from 7 patients with aortic stenosis and 10 patients with nonobstructive hypertrophic cardiomyopathy to compare left ventricular regional diastolic function. Left ventriculogram in the right anterior oblique projection was analyzed by the area method, and regional wall stress and regional area were computed for 4 regions in the mid-portion of the left ventricle. For each region, we assessed the percent area changes (normalized by end-diastolic regional area) and time constant for regional wall stress decrease during the isovolumic relaxation period. Regional non-uniformity during the isovolumic relaxation period was then evaluated by standard deviations for the percent area changes and for regional time constants of the 4 ventricular regions. In patients with hypertrophic cardiomyopathy, both the standard deviations for the percent area changes and the regional time constants were greater (P < 0.05) than those in patients with aortic stenosis, suggesting the presence of pronounced non-uniformity of regional relaxation in hypertrophic cardiomyopathy. The time constant of left ventricular pressure decrease during early relaxation phase was significantly greater (P < 0.01), and the early diastolic peak filling rate of the global left ventricle was significantly smaller (P < 0.05) in patients with hypertrophic cardiomyopathy. Thus, early diastolic left ventricular regional non-uniformity was more pronounced in hypertrophic cardiomyopathy than in aortic stenosis, which was associated with the impairment of relaxation and early filling of the global left ventricle. These findings suggest that different mechanisms are responsible for diastolic dysfunction in primary versus secondary myocardial hypertrophy.

Nicardipine to control mean arterial pressure during extracorporeal membrane oxygenation

The authors present the use of nicardipine to control mean arterial pressure (MAP) in a 19-month-old boy who required venoarterial extracorporeal membrane oxygenation for 11 days for treatment of hydrocarbon aspiration. Nicardipine is an intravenously administered dihydropyridine calcium channel antagonist whose primary physiological action includes vasodilatation. Unlike other calcium channel blockers, it has limited effects on the inotropic and dromotropic function of the myocardium. Nicardipine was started at 5 micrograms.kg-1.min-1 and within five min lowered the MAP from a maximum value of 108 mmHg back to the baseline range of 60 to 80 mmHg. Once the MAP had returned to baseline values, infusion requirements varied from 1 to 3 micrograms.kg-1.min-1 to maintain the MAP at 60 to 80 mmHg during the 11 days of ECMO. No increase in dose requirements were noted during the 11 days.

Pharmacologic drugs for controlled hypotension

Due to the risks of transfusion reactions and the transmission of infectious diseases, there has been increased interest in measures to limit intraoperative blood loss and avoid the need for homologous transfusion. Controlled hypotension is one technique that has been used to limit intraoperative blood loss. Several drugs have been used alone or in combination for controlled hypotension, including the inhalational anesthetics, direct acting vasodilators such as nitroglycerin and nitroprusside, beta adrenergic antagonists, and calcium channel blockers. Various drugs available to the clinician for controlled hypotension are reviewed.

Physiologic and pharmacologic factors that affect myocardial relaxation

Evaluation of the myocardial relaxation has become important in the last years. An impaired relaxation may precede contractile dysfunctions and even cause heart failure. To treat this impaired lusitropism it is necessary to properly assess the lusitropic state of the heart and understand how drugs affect the cellular mechanisms underlying myocardial relaxation (sarcoplasmic reticulum function, Ca2+ fluxes through the sarcolemma and myofilament Ca2+ sensitivity). Current information regarding these issues is provided in this review. The relative usefulness of the mechanical parameters used to evaluate the lusitropic state of the heart in experimental models applied in pharmacology will also be discussed.

Regional remodeling and nonuniform changes in diastolic function in patients with left ventricular dysfunction: modification by long-term enalapril treatment. The SOLVD Investigators

OBJECTIVES

The purpose of the present study was to assess the process of late regional remodeling and the changes in regional diastolic function at the base and apex of the left ventricle in patients with chronic systolic dysfunction.

BACKGROUND

Remodeling has been suggested to play an important role in the progression of left ventricular dysfunction and heart failure. However, the regional difference in the process of late remodeling and its relation to diastolic function remain unclear.

METHODS

In 32 patients with previous myocardial infarction and left ventricular ejection fraction < or = 35%, left ventricular hemodynamic and angiographic data were studied before and 1 year after randomization to conventional therapy with placebo (n = 12) or enalapril, 10 mg twice daily (n = 20). Left ventricular regional wall dynamics were analyzed in the basal and apical regions by the area method.

RESULTS

In the placebo group, left ventricular end-diastolic and end-systolic regional areas increased significantly over time at the base but were unchanged at the apex. At the base, the diastolic left ventricular pressure-regional area relation shifted rightward and the regional stiffness constant decreased (6.9 +/- 4.3 to 5.0 +/- 3.1 x 10(-3) mm-2, p < 0.05), indicating an increase in regional distensibility. At the apex, however, the diastolic pressure-regional area relation shifted upward slightly, and the regional stiffness constant increased from 11.5 +/- 4.4 to 14.4 +/- 5.6 x 10(-3) mm-2 (p = 0.08). The regional peak filling rate was maintained at the base but decreased at the apex (1,014 +/- 436 to 762 +/- 306 mm2/s, p < 0.05); further, the changes in regional peak filling rate during follow-up were inversely related to the changes in the regional stiffness constant (r = -0.78, p < 0.001) at the apex. In contrast, in the enalapril group, end-diastolic and end-systolic regional areas significantly decreased over time both at the base and at the apex. Diastolic pressure-regional area relations shifted leftward, but the regional stiffness constant and regional peak filling rate did not change significantly either at the base or at the apex.

CONCLUSIONS

These findings suggest that in patients with severe systolic left ventricular dysfunction, there was a regional difference in the process of late remodeling between the base and apex of the left ventricle, which was associated with nonuniform changes in regional diastolic function in the placebo group. The data also suggest that the nonuniform progression of regional remodeling and diastolic dysfunction was prevented by long-term enalapril treatment.

Changes in ventricular volume, wall thickness and wall stress during progression of left ventricular dysfunction. The SOLVD Investigators

To assess the long-term changes in cardiac function in asymptomatic patients with severe left ventricular dysfunction, left ventricular (cineangiography) and right ventricular (radionuclide angiography) function were assessed at baseline in 49 patients enrolled in the prevention arm of the Studies of Left Ventricular Dysfunction. After an average follow-up period of 12.4 months, 30 patients (11 randomized to the placebo group and 19 to the enalapril group) could be restudied to assess the progression of ventricular dysfunction. After 1 year of follow-up, the changes in heart rate, left ventricular end-diastolic and systolic pressure and right ventricular volumes were comparable in both groups. However, there were modest but opposite changes in left ventricular end-diastolic volume (+9 ml/m2 with placebo vs. -10 ml/m2 with enalapril, p < 0.05) and end-systolic volume (+5 ml/m2 with placebo vs. -13 ml/m2 with enalapril, p < 0.05). Mean systolic wall stress increased insignificantly in both groups, whereas ejection fraction increased from 29% to 31% in the placebo group and from 28% to 32% with enalapril (p = NS, placebo vs. enalapril). Even in asymptomatic patients with severe left ventricular dysfunction, there was a slow progression of left ventricular dilation. Enalapril administration appeared to slow this progression, but wall stress was not normalized by the treatment at the doses used in the study, indicating that at least one of the stimuli for further remodeling remained present.

Role of left ventricular regional nonuniformity in hypertensive diastolic dysfunction

OBJECTIVES

This study investigated 1) the role of left ventricular diastolic nonuniformity in hypertensive left ventricular diastolic dysfunction, and 2) the effects of a calcium channel antagonist on diastolic nonuniformity in hypertensive and normotensive subjects.

BACKGROUND

Augmented left ventricular diastolic nonuniformity contributes to diastolic dysfunction in hypertrophic cardiomyopathy. Impaired left ventricular diastolic function with preserved systolic function has been recognized in hypertension. Therefore, abnormal ventricular regional nonuniformity might also be involved in hypertensive diastolic dysfunction in a milder form of hypertrophy.

METHODS

Thirteen patients with established hypertension underwent radionuclide ventriculography before and after nifedipine administration. Indexes of left ventricular function were derived by computer analysis of the time-activity curve. After a computer subdivided the left ventricle into four regions, a time-activity curve of each region was constructed to determine an index of left ventricular diastolic nonuniformity. This index was calculated as the sum of the absolute values of time difference between global and regional peak filling in the septal, the apical and the lateral region. Ten normotensive subjects were studied for comparison. Echocardiography was performed in both groups.

RESULTS

The two groups were matched for age, gender, heart rate, echocardiographic dimensions and systolic function. In the hypertensive group, left ventricular diastolic filling indexes were impaired, with a negative correlation between peak filling rate and the diastolic nonuniformity index. Although the change in ejection fraction after nifedipine administration was similar in the two groups, the increase in peak filling rate was larger in the hypertensive patients. The diastolic nonuniformity index decreased after nifedipine in the hypertensive but not in the control group. This decrease correlated with improved peak filling rate in the hypertensive group.

CONCLUSIONS

In hypertensive patients with preserved systolic function, left ventricular diastolic nonuniformity increases, causing early diastolic dysfunction. Decreased diastolic nonuniformity after pharmacologic intervention contributes to lessened ventricular filling dysfunction, regardless of changes in loading conditions in hypertension. Thus, diastolic nonuniformity is an important determinant of left ventricular filling abnormality and might be a target of pharmacologic intervention in hypertensive patients.

Wall motion asynchrony is a major determinant of impaired left ventricular filling in patients with healed myocardial infarction

Left ventricular (LV) diastolic filling is impaired in hearts with healed myocardial infarction. Possible hemodynamic parameters related to impaired LV filling include left atrial pressure, time constant of isovolumic relaxation, chamber stiffness and wall motion asynchrony. Previous studies demonstrated univariate correlations between each of these parameters and LV filling. The current study was designed to compare relative importance of these parameters in patients with a myocardial infarction. Left ventriculograms with simultaneous LV pressure measurement were analyzed in 15 patients with a myocardial infarction and in 10 control subjects. Every frame of the left ventriculogram was divided into 8 segments and the volume of each segment was obtained frame-by-frame by planimetry and area-length method. Asynchrony was quantitated as the sum of areas of discrepancy between each segmental and global volume-time curve. Patients with myocardial infarction had greater asynchrony (20 +/- 2 vs 10 +/- 1%, p < 0.01), greater atrial filling fraction (46 +/- 4 vs 35 +/- 5%, p < 0.05) and slower peak early filling rate (2.5 +/- 0.1 vs 4.1 +/- 0.4 end-diastolic volume/s, p < 0.01) than the control subjects. Multiple regression analyses with hemodynamic variables (asynchrony, LV pressure at mitral valve opening, time constant of LV isovolumic pressure decrease and LV chamber stiffness constant) showed that asynchrony and LV pressure at mitral valve opening were significant determinants of LV filling in patients with myocardial infarction, whereas LV pressure at mitral valve opening was the only significant determinant in control subjects.

Cardioprotective effect of intracoronary nifedipine during percutaneous transluminal coronary angioplasty. A French double-blind cross-over multicentre study

The aim of this double-blind, placebo-controlled, cross-over study was to assess the cardioprotective effect of intracoronary nifedipine during percutaneous transluminal coronary angioplasty balloon occlusion. A balloon inflation without drug injection was initially made to ascertain that a shift of the ST segment (> or = 2 mm, 0.08 s after the J point) appeared (inclusion criterion). Two other balloon inflations were preceded by intracoronary injection of either 0.2 mg nifedipine or placebo, distal to the stenosis through the balloon catheter. The evaluation criteria were (1) time to ST segment shift, and (2) maximal amplitude of ST segment shift caused by balloon occlusion. Comparison of the data used an analysis of variance. Sixty-seven patients (mean age 54 +/- 8 years; 54 male, 13 female) were studied; 50 patients had 1-, 16 patients 2- and 1 patient 3-vessel disease. The dilated vessel was the left anterior descending coronary artery (n = 51), the right coronary artery (n = 12) and the left circumflex coronary artery (n = 4). Balloon inflation time was 100 +/- 31 s in the nifedipine group and 93 +/- 29 s in the placebo group. Five patients were excluded (procedure stopped after the first inflation in 1 and ST segment shift < 2 mm during the first inflation in 4). The time to 2-mm ST segment shift was longer in the nifedipine group than in the placebo group (62 +/- 40 s versus 51 +/- 40 s, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive detection of coronary artery disease by assessing diastolic abnormalities during low isometric exercise

The handgrip-apexcardiographic test (HAT) is a simple low-level (40% of maximal voluntary handgrip during 2 min) stress test which can detect left ventricular (LV) diastolic abnormalities. To determine whether it contributes to the diagnosis of coronary artery disease (CAD), HAT was obtained in 68 patients--47 with and 21 without angina pectoris--who prospectively underwent coronary arteriography. According to the highest or lowest individual values of diastolic apexcardiographic indices in 255 healthy volunteers, a pathologic or positive HAT was defined by the presence of at least one of the following new criteria: (1) A wave relative to total height of apexcardiogram during and/or after handgrip > 21%, (2) total apexcardiographic relaxation time (TART) during handgrip > TART at rest > 143 ms and/or TART corrected for the duration of diastole (TARTI) during handgrip < 0.14, or (3) diastolic amplitude time index (DATI), given by dividing TARTI and A wave relative to total diastolic amplitude of apex tracing during handgrip < 0.27. HAT was positive in 20 of 21 patients with single-vessel disease (sensitivity 95%), 21 of 24 patients with double-vessel disease (sensitivity 88%), and in 22 of 23 patients with triple-vessel disease (sensitivity 96%). Furthermore, HAT was positive in 20 of 21 (95%) patients without symptoms. Thus, the overall sensitivity of HAT for detecting CAD was 93%. This study is the first to demonstrate the high sensitivity of HAT in identifying patients with CAD with or without symptoms by assessing diastolic apexcardiographic abnormalities during low-level isometric stress. Thus, HAT potentially could become an additional simple diagnostic tool for noninvasive detection of patients with CAD.

Left ventricular relaxation in dilated cardiomyopathy: relation to loading conditions and regional nonuniformity

OBJECTIVES

The purpose of the present study was to investigate how loading conditions and regional nonuniformity affect left ventricular relaxation in dilated cardiomyopathy.

BACKGROUND

Left ventricular relaxation is impaired in dilated cardiomyopathy. It has been suggested that relaxation abnormality is related to loading conditions and regional nonuniformity in the diseased heart.

METHODS

Left ventriculography with simultaneous pressure manometry was performed in 10 patients with dilated cardiomyopathy before and during nitroprusside infusion. Ten normal subjects served as a control group. Left ventricular hemodynamics, regional wall motion (assessed by the area method) and regional wall stress (Janz method) were analyzed.

RESULTS

When compared with control subjects, the patients with dilated cardiomyopathy had a reduced left ventricular ejection fraction (p < 0.01) and prolonged relaxation time constants (p < 0.01). Left ventricular wall motion was both hypokinetic and asynchronous in the patient group. In addition, systolic regional wall stress was significantly greater, the time to peak wall stress was longer and the regional myocardial relaxation time constant was greater for each ventricular area assessed in the patient group (each p < 0.01). Administration of nitroprusside reduced left ventricular pressure and increased ejection fraction in the 10 patients with dilated cardiomyopathy. For each region, systolic regional wall stress and the time to peak wall stress decreased, and both regional hypokinesia and asynchrony lessened. These changes in loading conditions and regional nonuniformity were accompanied by an improvement in both regional and global ventricular relaxation that was significant, particularly during the early to midrelaxation phase when regional asynchrony was greatest.

CONCLUSIONS

These results suggest that myocardial relaxation is sensitive to loading conditions and regional nonuniformity in dilated cardiomyopathy and that load reduction can improve both relaxation and systolic performance of the left ventricle.

Left atrial and left ventricular diastolic function during acute myocardial ischaemia

OBJECTIVE

To study indices of diastolic left ventricular function during the first few seconds of myocardial ischaemia.

DESIGN

Isovolumic and total relaxation times and left atrial and left ventricular dP/dt were identified from high fidelity (micromanometer) pressure recordings in the left ventricle and left atrium during percutaneous transluminal angioplasty of the left anterior descending coronary artery.

PATIENTS

20 patients with isolated disease of the left anterior descending artery and normal left ventricular function.

RESULTS

The isovolumic relaxation time lengthened during the first seven to nine seconds of ischaemia; then it shortened by an average of 15% up to the twentieth second, initially as a result of increased left atrial contractility and subsequently because of impaired ventricular relaxation. Ventricular ischaemia resulted in impaired left ventricular diastolic compliance, as shown by an increase in the total relaxation time, before there was evidence of systolic impairment. Minimum dP/dt decreased progressively (by -37% at the twentieth second of ischaemia), whereas maximum dP/dt fell only after 20 seconds of ischaemia (by -11%).

CONCLUSIONS

Relaxation and filling of the left ventricle (indices of diastolic function) are more sensitive to myocardial ischaemia than myocardial contractility and systolic function. Left atrial contractility increases during left ventricular ischaemia.

Coronary vasodilatory action of elgodipine in coronary artery disease

The effects of intravenous elgodipine, a new second-generation dihydropyridine calcium antagonist, on hemodynamics and coronary artery diameter were investigated in 15 patients undergoing cardiac catheterization for suspected coronary artery disease. Despite a significant decrease in systemic blood pressure, elgodipine infused at a rate of 1.5 micrograms/kg/min over a period of 10 minutes did not affect heart rate and left ventricular end-diastolic pressure. The contractile responses during isovolumic contraction showed a slight but significant increase in maximum velocity (56 +/- 10 to 60 +/- 10 seconds-1; p less than 0.005), whereas the time constant of early relaxation was shortened from 49 +/- 11 to 44 +/- 9 ms (p less than 0.05). Coronary sinus and great cardiac vein flow increased significantly by 15 and 26%, respectively. As mean aortic pressure decreased, a significant decrease in coronary sinus (-27%) and great cardiac vein (-28%) resistance was observed, while the calculated myocardial oxygen consumption remained unchanged. In all, 69 coronary segments (including 13 stenotic segments) were analyzed quantitatively using computer-assisted quantitative coronary angiography. A significant increase in mean coronary artery diameter (2.27 +/- 0.53 to 2.48 +/- 0.53 mm; p less than 0.000001), as well as in obstruction diameter, (1.08 +/- 0.29 to 1.36 +/- 0.32 mm; p less than 0.02), was observed. The results demonstrate that elgodipine, in the route and dose described, induces significant vasodilatation of both coronary resistance and epicardial conductance vessels, without adverse effects on heart rate, myocardial oxygen demand and contractile indexes.

Ventricular relaxation and myocardial ischemia: a comparison of different models of tau during coronary angioplasty

This study compares the sensitivity and variability of four models of tau, the time constant of ventricular relaxation, to detect the presence of myocardial ischemia. High fidelity left ventricular pressure recordings were obtained in ten patients undergoing coronary angioplasty at baseline, during balloon inflation, and at recovery. Four models of tau were considered: 1) a semilogarithmic, zero asymptote model (TL), 2) a semilogarithmic model using data from the first 40 ms of isovolumic relaxation (T40), 3) an exponential non-zero asymptote model (TE), and 4) a derivative non-zero asymptote model (TD). TL, T40, and TE increased significantly during inflation and returned to near baseline values at recovery. TD showed no change during inflation. Comparisons of TL, T40, and TE using the derived relaxation half-time (T1/2), failed to reveal significant differences between the models at baseline, during inflation, or at recovery. The non-zero asymptote models were associated with a greater beat-to-beat variability than the semilogarithmic models. Thus, T1/2 using the semilogarithmic zero asymptote models (TL and T40) may be more useful and consistent when measuring the rate of isovolumic relaxation during myocardial ischemia.

Effects of acute K-strophantidin administration on left ventricular relaxation and filling phase in coronary artery disease

In 10 patients with coronary artery disease, preserved left ventricular (LV) performance and absence of previous myocardial infarction, the effects of an acute intravenous administration of k-strophantidin (0.005 mg/kg over 10 minutes) on selected parameters of both LV systolic and diastolic function, including relaxation, were evaluated. An increase in positive first derivative of LV pressure (dP/dt) and in the ratio between dP/dt and the pressure developed (dP/dt/P) (1,530 +/- 287) 1,600 +/- 329 mm Hg/s [p less than 0.05], and 30 +/- 6 to 34 +/- 8 s-1 [p less than 0.05], respectively) demonstrated the inotropic effect of k-strophantidin, whereas volumetric parameters of systolic function (end-systolic and stroke volume indexes, and ejection fraction) did not show any significant change. However, LV relaxation was impaired by k-strophantidin injection; in fact, mean values of T constant were significantly increased from 50 +/- 12 to 55 +/- 13 ms (p less than 0.01). Lowest LV and end-diastolic pressures increased from 8 +/- 4 to 11 +/- 4 mm Hg (p less than 0.05) and from 17 +/- 6 to 20 +/- 8 mm Hg (p less than 0.05), respectively. The end-diastolic volume and maximal rate of volumetric increase during the early and late filling phases were not modified by k-strophantidin. Mean aortic pressure increased from 110 +/- 10 to 120 +/- 12 mm Hg (p less than 0.001). Therefore, in patients with coronary artery disease and LV preserved performance, an acute intravenous administration of k-strophantidin appears to stimulate contractility and to worsen relaxation, and minimal LV and end-diastolic pressures.

Comparison of the cardiovascular effects of nifedipine and nicardipine in the presence of atenolol

A placebo controlled double blind crossover study was performed in 12 healthy volunteers to compare the cardiovascular effects of single oral doses of nifedipine (5, 10 and 15 mg) and nicardipine (20 and 30 mg) in the presence of atenolol 100 mg. Haemodynamic measurements were made by transthoracic electrical bioimpedance cardiography (TEBC) 2 h following drug administration during passive tilting, graded bicycle exercise (30-150 W) and recovery from exercise. In the absence of calcium channel blockade, atenolol reduced mean blood pressure, heart rate, and cardiac index, and increased stroke volume, peripheral resistance, pre-ejection period, and ventricular ejection time, particularly during and after exercise. In comparison with atenolol alone, addition of nifedipine or nicardipine reduced peripheral resistance but did not produce significant changes in stroke volume, cardiac output, dZ/dt [max], pre-ejection period (PEP). Ventricular ejection time (VET), PEP/VET, or Heather index at any point in the experiment. Similar reductions in peripheral resistance were produced by nifedipine 10 mg and nicardipine 20 and 30 mg. These apparently equivalent doses of nifedipine and nicardipine had similar effects on stroke volume, cardiac index, PEP/VET and Heather index. Thus the increases in ventricular performance previously demonstrated in association with nifedipine and nicardipine therapy were not observed in the presence of beta-adrenoceptor blockade. Under these conditions no important differences have been observed in the cardiovascular effects of these two calcium channel blockers.

Correlation of quantitative angiographic parameters with changes in left ventricular diastolic function after angioplasty of the left anterior descending coronary artery

This study evaluates the changes in left ventricular (LV) diastolic filling after percutaneous transluminal coronary angioplasty and the relation of such changes to quantitative angiographic measurements of the severity of coronary narrowings. Pulsed Doppler echocardiographic measurements were performed in 40 patients with single left anterior descending artery narrowing before, and 10 and 30 days after angioplasty. Minimal luminal diameter and percent diameter stenosis of coronary lesions were measured by computer-assisted quantitation. The ratio of early to late diastolic flow velocities (E/A ratio), time velocity integral of early diastolic filling period (Ei) and the ratio of early and late diastolic filling periods (Ei/Ai ratio) increased gradually after angioplasty. Minimal luminal diameter correlated significantly with the percent changes in E/A ratio (r = 0.59 at 10 days, r = 0.57 at 30 days), Ei (r = 0.53 at 10 days, r = 0.55 at 30 days) and Ei/Ai ratio (r = 0.41 at 10 days, r = 0.49 at 30 days). Percent diameter stenosis showed overall weaker correlations than minimal diameter with the percent changes in E/A ratio (r = 0.39 at 10 days, r = 0.32 at 30 days) and Ei (r = 0.38 at 10 days, r = 0.31 at 30 days). Thus, LV diastolic filling improves serially after coronary angioplasty in patients with 1-vessel disease. The magnitude of improvement in diastolic filling correlates better with minimal luminal diameter than percent diameter stenosis. Therefore, minimal luminal diameter is a better predictor of changes in Doppler transmitral flow parameters after angioplasty than percent diameter stenosis.

Alterations in endocardial vascular resistance after reperfusion in a low flow, high demand model of ischemia: effects of dipyridamole and WEB-2086, a platelet-activating factor antagonist

To determine if alterations in regional coronary vascular resistance could occur in the type of myocardial ischemia present in severe angina pectoris, regional perfusion and function were studied in 35 conscious sedated dogs. A stenosis producing severe hypokinesia of the perfused segment was created for 2 h on the left anterior descending coronary artery and 10 episodes of 1 min of high demand ischemia (atrial pacing at a rate sufficient to induce dyskinesia in the hypoperfused segment) were superimposed before reperfusion. The dogs were randomized into three treatment groups: control (n = 13), dipyridamole (n = 10) or WEB-2086 (n = 12), an antagonist of the effects of the endogenous platelet-activating factor. During stenosis, residual endocardial blood flow in the ischemic but nonnecrotic area averaged 0.72 +/- 0.14, 0.38 +/- 0.13 and 0.68 +/- 0.17 ml/min per g in the control, WEB-2086 and dipyridamole groups, respectively. Twenty-four hours after reperfusion, endocardial blood flow in the ischemic area was significantly lower in control dogs (1.04 +/- 0.15 ml/min per g) than in dogs treated with WEB-2086 (1.44 +/- 0.28 ml/min per g; p less than 0.03) or dipyridamole (3.00 +/- 0.83 ml/min per g; p less than 0.01). Accordingly, in control dogs, endocardial coronary vascular resistance in the ischemic area was increased after reperfusion from 85 +/- 11 to 124 +/- 27 mm Hg/(ml/min per g) (p less than 0.05) after 24 h. In contrast, coronary vascular resistance in the ischemic area remained unchanged in dogs receiving WEB-2086 (77 +/- 8 to 79 +/- 9 mm Hg/(ml/min per g); p = NS) and it decreased significantly in dogs receiving dipyridamole (72 +/- 8 to 44 +/- 8 mm Hg/(ml/min per g); p less than 0.01). Regional function after 24 h remained depressed in all three groups. These data indicate that low flow, high demand ischemia induces alterations in the subendocardial microvasculature. Such alterations in regional coronary vascular resistance might play a role in several forms of ischemic heart disease such as in severe angina, but they appear susceptible to improvement by therapeutic interventions that influence granulocyte and platelet activation.

The cardiovascular effects of oral nifedipine and nicardipine: a double-blind comparison in healthy volunteers using transthoracic bioimpedance cardiography

The cardiovascular effects of single oral doses of nifedipine (5 and 10 mg) and nicardipine (20 and 30 mg) were compared in a placebo controlled double-blind crossover study involving 8 healthy male volunteers. Two hours following drug administration stroke volume and cardiac index were measured non-invasively using transthoracic electrical bioimpedance cardiography during passive tilting, graded bicycle exercise, and recovery from exercise. Two separate experiments were performed in the absence of active drug to allow the reproducibility of the measurements to be assessed. Coefficients of variation (within experiment/between experiments) for cardiac index were 7.0%/19.9% at rest and 11.5%/9.3% at 180 W exercise. Both nifedipine and nicardipine increased stroke volume and cardiac index and reduced total peripheral resistance (mean blood pressure/cardiac index) at all times in the experiment. Reductions in peripheral resistance were similar for nifedipine 10 mg and nicardipine 20 mg but in these doses slightly larger increases in heart rate were produced by nifedipine, and in stroke volume and cardiac index with nicardipine. The study shows that the cardiovascular effects of nifedipine and nicardipine can be detected using impedance cardiography which is a simple, safe, and inexpensive technique. The differences between the effects of the two drugs were small. Although some were of statistical significance and are consistent with a less marked cardiodepressant effect for nicardipine, the clinical importance of these observations is uncertain. Further studies to examine the effect of oral nifedipine and nicardipine in patients with impaired ventricular function may be helpful in clarifying this tissue.

Effects of long-term xamoterol therapy on the left ventricular mechanical efficiency in patients with ischemic heart disease

Myocardial oxygen uptake and an index of mechanical left ventricular efficiency were determined in basal conditions or during prolonged therapy with the new beta 1-adrenoceptor partial agonist xamoterol in 16 patients with mild to moderate ischemic heart failure. During xamoterol therapy, left ventricular end-diastolic pressure decreased from 24.4 +/- 6.5 to 17.8 +/- 8.6 mm Hg (P less than 0.01) and the isovolumic index of inotropic state (dP/dt)/DP40 increased by 14% (P less than 0.01). The heart rate increased slightly and the mean systolic and peak systolic wall stress also tended to increase (+ 7%; NS) but myocardial oxygen uptake (14.1 vs 14.7 ml/min; NS) and the index of efficiency (8.77 +/- 3.44 to 8.82 +/- 4.27; NS) were not significantly modified. In conclusion, prolonged therapy with xamoterol was not accompanied by a deterioration in the mechanical efficiency of the ventricle, even in patients with ischemic heart disease.

Effect of temperature on rate of left ventricular pressure fall in humans

The time constant (T) of left ventricular pressure fall is widely used as an index of ventricular "relaxation". It is not known whether its rate limiting step is deactivation, an enzymic energy consuming reaction whose rate is therefore sensitive to temperature, or elastic recoil. To distinguish between these possibilities, the time constant was measured by simple logarithmic (Tlog) and exponential (Texp) methods in 12 patients during cooling before coronary artery grafting. Ventricular loading conditions were altered by transfusion from bypass to maintain arterial and left atrial pressures constant in individual patients, though heart rate fell from 86 (8.4) to 68 (10) beats/min. Tlog increased from 49 (10) ms mean (SD), at 37 degrees C to 86 (15) ms at 31 degrees C, and Texp from 63(14) at 37 degrees C to 112 (23) ms at 31 degrees C with intermediate values at 34 degrees C. Texp proved sensitive to "noise" at low temperatures, but the overall change in Tlog with temperature was 9% per degree C--considerably less than that observed experimentally for the rate of tension decline of isolated myocardium, and possibly itself an overestimate because of the concomitant fall in heart rate. The relatively small effect of temperature on Tlog in humans, associated with a considerable load sensitivity appearing under hypothermic conditions, does not favour simple dependence on deactivation as the rate limiting step of left ventricular pressure fall, but suggests that its determinants may be complex.

Effects of nifedipine on left ventricular distensibility, relaxation and filling dynamics during pacing-induced myocardial ischemia

Diastolic left ventricular properties were assessed in 8 patients with coronary artery disease at rest and during postpacing states before and after nifedipine (10 mg sublingually). Typical anginal pain developed in all patients during pacing tachycardia before but not after nifedipine. Postpacing increases in end-diastolic pressure (10 +/- 5 [mean +/- standard deviation] to 23 +/- 9 mm Hg) and volume (99 +/- 29 to 113 +/- 27 ml) were greatly attenuated with nifedipine (13 +/- 7 and 97 +/- 22 ml, respectively). These responses were associated with normalization of postpacing shifts of the ventricular diastolic pressure-volume curve upward or more to the right. The time constant of ventricular relaxation was prolonged by pacing tachycardia (44 +/- 10 to 62 +/- 5 ms) and was reduced to the control level in postpacing beats after nifedipine. The peak rate of early ventricular filling was affected neither by pacing stress nor by nifedipine. When regional myocardial function was expressed by a radial coordinate system, the nonischemic segment responded to the control pacing with an increase in end-diastolic length and comparable augmentation of the stroke excursion, while the ischemic segment showed a marked reduction in stroke excursion with end-diastolic length unchanged. Thus, the diastolic pressure-length relation moved up to the higher portion of the single curve in the nonischemic segment, while it shifted directly upward in the ischemic segment. These responses were markedly attenuated with nifedipine.(ABSTRACT TRUNCATED AT 250 WORDS)

Usefulness of negative dP/dt upstroke pattern for assessment of left ventricular relaxation in coronary artery disease

It has been reported that regional asynchrony due to acute ischemia disturbs the exponential nature of left ventricular (LV) pressure reduction and may alter the pattern of (-)dP/dt upstroke curve. If LV pressure decreases exponentially during the isovolumic relaxation period (P = Ae-t/T + B, where A and B = constants, t = time and T = time constant), the (-)dP/dt upstroke curve should also be exponential and upward-convex because dP/dt = A(-t/T)e-t/T. To test this theory in humans, the LV (-)dP/dt upstroke curve was analyzed in 9 normal subjects, 12 patients with effort angina pectoris (AP) and 15 with old myocardial infarction (MI) under the basal conditions. The (-)dP/dt upstroke was convex-upward in all normal subjects, but convex-downward in 9 of 12 patients with AP and in all patients with MI, which suggests nonexponential decrease in LV pressure in the groups with AP and MI. The dP/dt (20/60), which is the ratio of the (-)dP/dt value at 20 ms after peak (-)dP/dt to that at 60 ms after peak (-)dP/dt, was significantly lower in the group with AP (1.70 +/- 0.07) and in the group with MI (1.61 +/- 0.13) than in normal subjects (2.08 +/- 0.18) (p less than 0.005). This indicates that (-)dP/dt upstroke 20 to 60 ms after peak (-)dP/dt increases more slowly in the groups with AP and MI than in normal subjects. Theoretical consideration showed that such a slower increase of the upstroke resulted from impaired early to midrelaxation.(ABSTRACT TRUNCATED AT 250 WORDS)

Focus on diastolic dysfunction: a new approach to heart failure therapy

1. Although heart failure is commonly associated with depressed systolic function, there is increasing evidence that impaired diastolic performance is also universally present and might be a key determinant of symptoms, physical capacity and even survival in some subsets of patients. 2. Reduced diastolic distensibility increases cardiac filling pressure not only at rest, but even more during exercise when diastolic filling time is reduced. The increases in filling pressure and diastolic wall stress lead to pulmonary congestion and subendocardial ischaemia, it also triggers myocardial hypertrophy and a detrimental remodelling of the ventricular cavity. Perhaps even more importantly, impaired ventricular distensibility limits the use of the Frank-Starling mechanism, impairing systolic pump function and cardiac output adaptation during exercise. Therapies able to improve the distensibility of the ventricle are, therefore, desirable in heart failure. 3. Nitrates, angiotensin converting enzyme (ACE) inhibitors and diuretics may indirectly increase left ventricular chamber compliance by their effects on the right side of the heart. Cardiac glycosides do not improve myocardial relaxation and may even cause diastolic contracture at toxic doses. The new beta 1-adrenoceptor partial agonist, xamoterol, on the other hand, consistently lowers left ventricular filling pressure at rest and during exercise, and produces an increase in left ventricular dynamic compliance through the direct lusitropic effect of beta 1-adrenoceptor stimulation. These beneficial effects are maintained during prolonged therapy and also appear sufficient to slow the remodelling of the ventricular cavity. The improvement in symptoms and in exercise tolerance observed during xamoterol (Corwin, Carwin, Corwil, Xamtol, ICI 118,587) therapy might, therefore, be related to the improvement in left ventricular diastolic distensibility induced by this drug.

The effects of acute ischemia on the isovolumic index

The isovolumic index is the ratio of the duration of isovolumic contraction (IVC) and relaxation (IVR) divided by ejection time (ET), and has been proposed as a more sensitive descriptor of ventricular performance than the systolic time index, which ignores the period of isovolumic relaxation. To determine the effects of acute ischemia on these indices, IVC, IVR, and ET were measured in seven open-chest dogs instrumented with high-fidelity micromanometers and ultrasonic crystals and subjected to a 10-second period of coronary occlusion. Fractional shortening was significantly impaired (18.4 +/- 6.9% vs 1.9 +/- 7.3%, p less than 0.001) during coronary occlusion. ET was unaffected by the brief ischemia, whereas IVC time showed directional shortening that attained statistical significance (55 +/- 7 msec control vs 50 +/- 6 msec, p less than 0.01) at 8 to 10 seconds. IVR time was prolonged by occlusion, significantly so at 6 to 8 seconds (72 +/- 26 msec control vs 88 +/- 22 msec, p less than 0.01) and at 8 to 10 seconds (81 +/- 19 msec, p less than 0.05). The systolic time index showed no deterioration during ischemia, whereas the isovolumic index did not show directional prolongation. Assessment of IVC, IVR, and ET at the time of the maximal change in the isovolumic index revealed significant changes of IVC and IVR (each p less than 0.05 vs control), though ET and the systolic time index were unchanged. Through incorporation of IVR, the isovolumic index was more sensitive to acute brief ischemia than the systolic time index.

Doppler echocardiographic evaluation of the effect of atrial pacing-induced ischemia on left ventricular filling in patients with coronary artery disease

Very little is known about the effects of acute myocardial ischemia on left ventricular filling. Previous studies of these effects have been of limited value because they were performed with 1) imaging techniques that, like cineventriculography or radionuclide ventriculography, do not allow beat to beat monitoring of left ventricular filling throughout the entire ischemic attack; and 2) exercise, which, even if effective in inducing myocardial ischemia in patients with coronary artery disease, also considerably shortens cycle length, thus leading to additional nonischemic filling alterations. To overcome these limitations, left ventricular filling was studied by means of Doppler echocardiographic evaluation of transmitral flow velocities before and immediately after rapid atrial pacing in 17 patients. Eight patients had coronary artery disease but did not develop ischemia (ST depression greater than or equal to 1.5 mm) during atrial pacing (Group 1) whereas nine had coronary artery disease and developed ischemia during atrial pacing (Group 2). No differences were observed from rest to postpacing in any of the filling variables considered in Group 1 patients. In contrast, a significant rearrangement of left ventricular filling occurred during ischemia in Group 2 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of changes in coronary stenosis on left ventricular diastolic filling assessed with pulsed Doppler echocardiography

To determine the effects of changes in coronary stenosis on left ventricular diastolic filling, diastolic filling was serially examined before and after percutaneous transluminal coronary angioplasty using pulsed Doppler echocardiography in 50 patients with stable exertional angina pectoris. Peak rapid filling velocity and the ratio of peak atrial filling to peak rapid filling velocities were measured from the transmitral flow velocity pattern before and 2 and 9 days after coronary angioplasty. Peak rapid filling velocity increased and the ratio of peak atrial filling to peak rapid filling velocities decreased gradually after coronary angioplasty. The improvement in left ventricular diastolic filling was greater in patients with severe (greater than 90%) coronary stenosis than in patients with mild (less than or equal to 90%) coronary stenosis. In the long-term follow-up period, the improved left ventricular diastolic filling worsened in only 11 patients with marked progression to greater than 90% coronary stenosis. Thus, left ventricular diastolic filling improved gradually after coronary angioplasty, possibly reflecting post-ischemic "stunned" myocardium. Serial examinations of left ventricular diastolic filling with pulsed Doppler echocardiography may be a means of noninvasively assessing the temporal changes in the coronary stenosis and predicting the occurrence of coronary restenosis after coronary angioplasty.

Altered response of reperfused myocardium to repeated coronary occlusion in dogs

It is hypothesized that myocardium subjected to a 5 minute period of coronary occlusion and a 30 minute period of reperfusion has latent abnormalities that become overt when the reperfused myocardium is "challenged" by a subsequent coronary occlusion. This hypothesis is clinically relevant because reperfused myocardium is frequently subjected to recurrent ischemia, as in patients with unstable angina, vasospastic angina or recurrent thrombosis after initial coronary occlusion and thrombolysis. In 19 open chest dogs, the response of regional myocardial function to brief coronary occlusions was studied. Systolic wall thickening and diastolic thinning were measured using a specially developed miniature 5 MHz echocardiographic transducer fixed to the epicardium by suction. All 19 dogs underwent an initial "challenge" coronary occlusion (30 seconds). Thereafter, the control group (n = 8) underwent no intervention for 30 minutes, while the intervention group (n = 11) underwent 5 minutes of coronary occlusion followed by 30 minutes of reperfusion. All dogs were then subjected to a second "challenge" coronary occlusion (30 seconds). In the control group, responses to the second challenge occlusion were the same as to the first occlusion. In the intervention group, regional and global systolic function and myocardial perfusion after the 5 minute coronary occlusion intervention returned to baseline levels, but the response to the second challenge coronary occlusion was significantly different in the intervention group.(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular diastolic filling abnormalities in left anterior descending disease

Reduced left ventricular diastolic filling (DF) has been noted in coronary disease (CD) patients with normal left ventricular systolic function (NLVF). However, previous studies have included patients with regional wall disease, hypertension, or left ventricular hypertrophy. In the absence of these factors, only a subgroup of patients who had greater than 75% luminal obstruction of the left anterior descending artery (LAD) demonstrated DF abnormalities. Using 60 frames/sec biplane contrast ventriculography, we evaluated the left ventricular filling curve and its derivative in 21 patients with normal coronary arteries and NLVF (group 1), 17 CD patients with NLVF and no LAD disease (group 2), and 18 patients with LAD disease and NLVF (group 3). The peak filling rate (PFR) as end diastolic volumes/sec (EDV/S) was reduced in group 3 patients (group 3: 3.00 +/- 0.51 EDV/S vs group 1: 3.59 +/- 0.84 EDV/S, p less than .05; and group 2: 3.61 +/- 0.91 EDV/S, p less than .05). There was marked overlap in the PFR's between the normal and LAD group. DF may be normal in CD patients with NLVF in the absence of LAD disease. LAD patients have abnormal DF, but these abnormalities lack predictive valve.

Myocardial protection by intracoronary nicardipine administration during percutaneous transluminal coronary angioplasty

To determine if the calcium antagonist nicardipine protects the myocardium against ischemia, myocardial lactate, hypoxanthine and prostanoid function was studied in 12 patients during percutaneous transluminal coronary angioplasty (PTCA). Values were obtained before balloon inflation and during 4 minutes after deflation. Intracoronary injection of 0.2 mg of nicardipine distal to the stenosis was done randomly before the first or second inflation; the other inflation served as a control. One minute after deflation, coronary sinus flow levels were similar during the nicardipine and control procedure (161 +/- 61 vs 159 +/- 72 ml/min); lactate (-9 +/- 21% vs -17 +/- 21%, p less than 0.025) and hypoxanthine production (-107 +/- 85% vs -218 +/- 153%, p less than 0.05) were less severe after nicardipine pretreatment than after control. All patients reverted to lactate extraction 4 minutes after inflation plus nicardipine infusion, whereas lactate was still produced 4 minutes after control inflation. No significant changes in thromboxane B2 or prostacyclin levels were observed in the coronary sinus 1 minute after inflation, but higher arterial thromboxane B2 values were observed after control inflation than after inflation with nicardipine infusion (median values 169 vs 78 pg/ml, p less than 0.05). In conclusion, intracoronary infusion of nicardipine reduced signs of ischemia and alterations in prostanoid handling after coronary occlusion. The mechanisms of myocardial protection appeared unrelated to coronary sinus blood flow changes or to a systemic effect of nicardipine.

Effects of verapamil and nifedipine on rate of left ventricular relaxation in coronary arterial disease patients

We have evaluated the effects of nifedipine and verapamil on rate of left ventricular relaxation in 26 patients having coronary arterial disease with normal ejection fraction and normal left ventricular contractility. None of the patients had myocardial infarction. All patients showed normal contractile indices and abnormally high values of T constant, neg, dP/dt and left ventricular protodiastolic pressure, suggesting an impairment of left ventricular relaxation. Nifedipine, injected intravenously (15 micrograms/kg) in 14 patients induced a significant reduction of afterload parameters and an increase of contractility. Nifedipine also improved left ventricular relaxation, as it induced a reduction of the T constant from 42 +/- 2 msec to 33 +/- 2 msec (P less than 0.01). It induced a tendency to a reduction of negative dP/dt and protodiastolic pressure without reaching statistical significance. Verapamil, injected intravenously in the remaining 12 patients (0.1 mg/kg as a bolus followed by chronic infusion of 0.005 mg/kg/min for 3 min) induced a reduction of the T constant from 43 +/- 10 to 37 +/- 6 msec (P less than 0.01). It reduced the negativity of dP/dt from 2302 +/- 273 to 2021 +/- 252 mm Hg/sec (P less than 0.05) and of left ventricular protodiastolic pressure from 3.2 +/- 1.4 to 1.5 +/- 1.1 mm Hg (P less than 0.01). Verapamil, like nifedipine, reduced the afterload parameters although to a lesser extent. It did not substantially affect the left ventricular contractility. These data suggest that abnormalities of left ventricular relaxation may precede changes in systolic function and that nifedipine and verapamil favourably modify the indices of left ventricular diastolic function in patients with coronary arterial disease.

Impaired regional diastolic distensibility in coronary artery disease: relations with dynamic left ventricular compliance

The regional left ventricular distensibility and its relations with the dynamic left ventricular chamber compliance were studied in 11 normal subjects and in 30 patients with coronary artery disease. The regional peak filling rates were calculated from angiographic data in eight ventricular segments and used as an index of regional distensibility. A depressed global peak filling rate was observed in only 30% of the patients with angina pectoris, but regional abnormalities in peak filling rate were detected in 75% of these patients. A relation between alterations in regional peak filling rate and left ventricular compliance was evident in these patients. Despite comparable end diastolic volume and pressure (10 +/- 2 mm Hg vs. 10 +/- 3 in normal subjects; not significant), the patients with angina pectoris, whose ventricle had at least three segments with a reduced peak filling rate, had indeed significant increases in mean left ventricular filling pressure (14 +/- 4 mm Hg vs. 8 +/- 3 in normal subjects; p less than 0.01) and upward shifts of their left ventricular pressure-volume relation during rapid filling. Conversely, an increase in regional peak filling rate produced by intravenous administration of the calcium antagonist nicardipine in a subgroup of patients with poor diastolic function was accompanied by a reduction in mean left ventricular filling pressure and by a downward shift of the early diastolic left ventricular pressure-volume relation. It is concluded that even in the absence of clinical signs of ischemia and of a previous myocardial infarction, large areas with impaired distensibility are frequently present in patients with angina pectoris.(ABSTRACT TRUNCATED AT 250 WORDS)