Influence of coronary occlusion during PTCA on end-systolic and end-diastolic pressure-volume relations in humans

Mechanisms, diagnosis, and treatment of diastolic heart failure

Diastolic heart failure, in the absence of LV systolic dysfunction, is a common clinical condition that can be demonstrated in as many as one third of patients with congestive heart failure. Diastolic dysfunction caused by abnormalities in LV filling can be a result of many pathologic conditions, including hypertrophy, infiltrative cardiomyopathies, or myocardial ischemia. The major physiologic determinants of LV filling can be divided into cellular mechanisms, hemodynamic characteristics, and hormonal influences. Cellular mechanisms for impaired LV inactivation are determined by the handling of calcium within the myocyte during excitation-contraction-relaxation coupling. The hemodynamic characteristics of LV diastolic filling are determined by loading conditions, the time constant of isovolumic relaxation, heart rate, ventricular nonuniformity, pericardial restraint, myocardial elasticity, chamber compliance, and coronary blood flow. The sympathetic nervous system and the renin-angiotensin system are important modulators of diastolic filling, directly or indirectly. The diagnosis of heart failure is confirmed by a combination of clinical tests including invasive and noninvasive techniques, each of which has advantages and disadvantages. Treatment of medical conditions in which diastolic heart failure is a prominent component include pharmacotherapy with calcium channel antagonists, beta-adrenergic blocking agents, diuretic agents, and angiotensin-converting-enzyme inhibitors. Certain conditions associated with diastolic filling abnormalities such as pericardial disease or severe ischemic heart disease may be best managed by surgical or percutaneous intervention. Future research will include further delineation of the cellular mechanisms of active myocardial relaxation and clinical investigation into treatment directed at improving outcome.

Estimation of left ventricular compliance using on-line echocardiographic automated border detection and pressure data

The end-diastolic pressure-volume relationship can be used to describe left ventricular (LV) compliance. The objective of this study was to utilize measurements of LV cavity area by echocardiographic automated border detection and pressure data to estimate the end-diastolic pressure-volume curve in an isolated heart preparation where true volume could be measured by an intraventricular balloon. Six dog hearts were excised for placement of an intraventricular balloon and a micromanometer catheter and perfused in an ex vivo circuit. Mid-ventricular short-axis images were used to measure cross-sectional area by automated border detection while LV volumes were increased from 5 ml to maximal volume (30-40 ml) in each preparation. Simultaneous area and pressure data were recorded on a computer workstation through a customized interface with the ultrasound system. Three runs of varying LV volumes at 1 ml increments were performed on each of 6 hearts for a total of 1,080 simultaneous measurements. Pressure-volume and pressure-area curves were analyzed by linear regression analyses, the slope of which was used to estimate compliance. End-diastolic pressure-area and pressure-volume relationships were significantly correlated with mean r = 0.97 +/- 0.02 (p < 0.001) from individual hearts. The slopes which served to estimate compliance of the individual pressure-area and pressure-volume curves were similar and differed by only 7 +/- 4%. A similar correlation was observed by second order regression analyses with r = 0.97 +/- 0.01 (p < 0.001) for pressure-area and r = 0.98 +/- 0.01 (p < 0.001) for pressure-volume relationships.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventricular remodeling and infarct expansion

Infarct expansion, defined as an alteration in the ventricular topography due to thinning and lengthening of the infarcted segment, develops within the first few hours of the acute symptoms, mostly in patients with a large, transmural, anterior myocardial infarction. Shape changes, peculiar to risk region location and due to disparity in regional ventricular architecture, could be posited as the first step in the process of infarct expansion, with various cellular mechanisms contributing to subsequent continued early and late ventricular dilation. Because the increase in left ventricular volume is expected to be linearly dependent on the extent of the infarction, limiting infarct size, by thrombolysis, would proportionally reduce enlargement of the cavity. The effect of thrombolysis on left ventricular volume, however, seems not to be completely accounted for by the lessening effect of reperfusion on infarct size, because data suggest a restraining effect of reperfusion on the process of ventricular dilation in addition to the lessening effect on infarct size. If this turns out to be true, then the achievement of a patent vessel even beyond the time period when that patency may be expected to salvage myocardium would be further justified. Theoretical predictions substantiate the potential effectiveness in restraining ventricular dilation of stiffening of the necrotic region alone, independently of myocardial salvage in infarcted patients. The process of progressive ventricular dilation involves not only a primary alteration in function of the infarcted region, but also a time-dependent secondary change in the noninfarcted tissue itself, finalized to restore stroke volume despite a persistently depressed ejection fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Diastolic heart function--pathophysiology, characterization, and therapeutic approaches

In recent years diastolic cardiac function has attracted increasing attention since parameters of diastolic function were found to be altered earlier or more specifically than parameters of systolic function. Diastolic cardiac function is determined by both active (muscular relaxation, redistribution of calcium, synchronization, etc.) and passive (myocardial structure, fibrosis, etc.) factors. As a consequence, a comprehensive assessment of diastolic cardiac function cannot be based on one single parameter. For a complete analysis of diastolic function it is necessary to perform invasive diagnostic procedures involving the measurement of atrial and ventricular pressures, as well as the registration of volume changes with a high time resolution. In addition, it is necessary to measure wall thickness and ventricular configuration, so that apart from filling parameters the stress-strain relationship can be obtained. Noninvasive techniques (Doppler echocardiography, radionuclear ventriculography, apexcardiography) may suggest alterations in diastolic function as well. They ought to be complemented by additional diagnostic procedures (pulmonary pressure, stress testing, etc.). Therapy must consider potentially harmful effects on diastolic function parameters, particularly if changes in myocardial oxygen consumption may result (heart rate, parietal wall stress). Calcium antagonists (verapamil, diltiazem, nifedipine), phosphodiesterase inhibitors (milrinone), beta-adrenergic agonists and antagonists with vasodilating effects (e.g., celiprolol) all have beneficial effects on diastolic myocardial function. A range of diastolic function parameters is being reviewed in the following paper. Their role in the estimation of cardiac function and their responsiveness to therapy in hypertrophy, cardiomyopathy, and coronary heart disease is being discussed.

Pulmonary artery hemodynamic response to proximal balloon dilatation of a large dominant right coronary artery

The human right ventricle has a relatively low tolerance to even short periods of ischemia. During angioplasty of the right coronary artery, pulmonary artery pressure typically rises due to an increase in right ventricular afterload caused by left ventricular dysfunction during ischemia. We have presented two cases of angioplasty in the early proximal portion of a large, highly dominant right coronary artery. Pulmonary artery and systemic pressure fell during balloon inflation probably secondary to acute severe right ventricular failure, though an interaction with left ventricular dysfunction cannot be excluded. These observations do emphasize the hemodynamic and combined ventricular consequences of proximal angioplasty in a large, dominant right coronary artery, particularly in the setting of preexisting left ventricular dysfunction.

Tedisamil (KC 8857) is a new specific bradycardic drug: does it also influence myocardial contractility? Analysis by the conductance (volume) technique in coronary artery disease

To determine whether inotropism influences the bradycardic action of tedisamil, hemodynamic assessment was performed in 13 patients with ischemic coronary artery disease including analysis of end-systolic pressure-volume relationships after an infusion of tedisamil, 0.3 mg/kg, at rest, and during paced tachycardia stress. Slope Emax fell by 14% at rest (13 patients) and by 10% during tachycardia (6/13 patients), whereas loops of end-systolic pressure-volume relationships moved rightward; all parameter changes indicated a lack of significant inotropism loss with tedisamil (p > 0.05). Although the mean heart rate decreased from 77.5 to 64.7 beats/min and QTc duration increased by 14% (p < 0.05), filling pressure and dp/dtmin remained unchanged and vascular resistance increased by 30%. Parameters of left ventricular pump function (ejection fraction, stroke volume, left ventricular efficiency) decreased slightly (between 3% and 13%), whereas left ventricular volumes increased (end-diastolic volume by 6%, end-systolic volume by 23%). The respective parameter changes during tachycardia were comparable in tendency, and angina could no longer be induced during postdrug pacing stress. We concluded that the bradycardic effects of tedisamil are selectively generated without impairing either ventricular pump function or contractility in a clinically relevant fashion, whereas the postdrug anginal threshold appears elevated. Thus tedisamil can be used safely in ischemic coronary artery disease.

Inosine--a natural modulator of contractility and myocardial blood flow in the ischemic heart?

The energetic role of inosine (INO) remains controversial. The aim of the present study was first to test whether endogenous INO consumption/production correlates with regional myocardial contractile performance and second to test whether locally increased levels of INO influence contractility and blood flow in severely ischemic myocardium. Fentanyl-anesthetized dogs with implanted sonomicrometry crystals and independently perfused left anterior descending coronary arteries were studied. Two relatively load-independent indexes of regional myocardial contractility derived from left ventricular pressure-segment length loops were used: the regional stroke work-end-diastolic segment length relationship (Wr/L(ed)) and the end-systolic pressure-segment length relationship (Plv/L(es)). Very good correlations between myocardial contractile performance (as measured by the slope of the regional Wr/L(ed) relationship) and endogenous INO consumption/production under both nonischemic and ischemic conditions were found. Ischemia severely depressed contractility, significantly shifting rightward the Wr/L(ed) and Plv/L(es) relationships. INO infused into the left anterior descending bypass, in a concentration of 600 to 800 mumol/L, partially restored contractile performance as evidenced by a significant leftward displacement of both relationships. Wr, measured at a common maximum L(ed), increased significantly by 61 +/- 5%. Border-zone collateral flow (microspheres) increased by 35 +/- 7% within the endocardial segments and by 34 +/- 9% in the epicardial segments, but no increase in flow in the ischemic region was measureable. With the current emphasis on recanalization with thrombolytic therapy and considering the apparent safety of INO, this naturally occurring nucleoside might prove to be a useful adjunctive agent in the treatment of acute myocardial ischemia.

Reperfusion of the infarct-related coronary artery limits left ventricular expansion beyond myocardial salvage

Previous echocardiographic data from the Gruppo Italiano per lo Studio della Streptochinasi nell' Infarto Miocardico (GISSI 1) trial suggest that the relation between left ventricular end-systolic volume and infarct size could be altered by thrombolysis, which would exert a restraining effect on end-systolic volume beyond its reducing effect on infarct size. Thus in 63 patients with one-vessel disease and a recent anterior myocardial infarction, we tested at angiography (1) if perfusion of the anterior descending coronary artery exerts any restraining effect on end-systolic volume above and beyond infarct size reduction and (2) if ejection fraction reflects such an additional, beneficial difference in the ventricular remodeling process. End-systolic volume was calculated using the Dodge method and the right anterior oblique projection, while infarct size was quantified according to the number of ventricular radii whose percent shortening fell below the mean -2 SD of a group of normal individuals. Patients were then divided into two groups according to the perfusion status of the vessel using Thrombolysis in Myocardial infarction (TIMI) criteria (TIMI grade 0 to 1: nonperfused vessel, 27 patients; TIMI grade 2 to 3: perfused vessel, 36 patients). For both groups there was a significant linear relation (p less than 0.001) between end-systolic volume and infarct size; as in our echocardiographic data, the regression lines relating volume to infarct size showed a different slope in the two populations so that, for large and matched infarcts, end-systolic volume was smaller in patients with a perfused vessel (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Impairment of left ventricular function during coronary angioplastic occlusion evaluated with a nonimaging scintillation probe

Impairment of left ventricular function during controlled myocardial ischemia induced by coronary angioplasty has been reported from angiographic and echocardiographic studies. Ejection fraction, peak ejection, peak filling rates, and end-systolic and end-diastolic volumes were investigated before, during and after coronary occlusion on-line with a nonimaging scintillation probe. The study consisted of 18 patients (mean age 59 +/- 10 years) with coronary artery stenosis of greater than 70%. During balloon inflation of 60 seconds' duration, coronary occlusion pressure was 31.6 +/- 12 mm Hg. There was no significant change in heart rate. Delay between first and second dilatation was 109 +/- 63 seconds. Ejection fraction decreased from 53 +/- 16 to 40 +/- 12% (first dilatation, p less than 0.01) and to 39 +/- 14% (second dilatation, p less than 0.01) and recovered to 51 +/- 16% 5 minutes after the second dilatation. Peak ejection rate was significantly reduced during the first and second balloon inflations. Peak filling rate decreased from 2.5 +/- 0.8 to 2.0 +/- 0.7 end-diastolic volume.s-1 (first dilatation, p less than 0.01) and to 1.8 +/- 0.7 end-diastolic volume.s-1 (second dilatation, p less than 0.01) and remained reduced at 2.2 +/- 0.7 end-diastolic volume.s-1 (p = not significant) at 5 minutes after the second dilatation. End-systolic and end-diastolic volumes increased significantly during the first and second dilatations and returned to normal after dilatation. It is concluded that short, controlled myocardial ischemia during coronary angioplasty leads to a decrease in systolic and diastolic left ventricular function. Sequential dilatations do not further decrease function if a sufficient interval is kept.

Pressure-volume analysis as a method for quantifying simultaneous drug (amrinone) effects on arterial load and contractile state in vivo

Pressure-volume relation analysis was used to independently quantify changes in ventricular contractile performance and vascular loading in intact anesthetized dogs before and after a single bolus of intravenous amrinone. Ventricular systolic property changes were characterized by the end-systolic elastance (Ees = slope of the end-systolic pressure-volume relation) and arterial properties by the effective arterial elastance (Ea = end-systolic pressure/stroke volume ratio). Pressure-volume data were obtained by the conductance catheter technique with loading varied by transient inferior vena cava occlusion. Amrinone induced a 27% increase in ejection fraction at 10 min (from 44% to 56%) as a result of both a significant rise in contractility (mean Ees 4 +/- 2 to 6 +/- 3 mm Hg/ml, p less than 0.001) and simultaneous reduction in arterial loading (Ea reduction from 6 +/- 2 mm Hg/ml to 5 mm Hg/ml, p less than 0.001). Over the subsequent 30 min, Ea revealed a significant recovery toward baseline, whereas Ees was less altered. Mean percent changes (% delta) in both variables were linearly correlated: % delta Ea = -1.6 x % delta Ees + 3.1, r = 0.96, p less than 0.001. In addition to separating ventricular from vascular property changes, the pressure-volume coupling framework was used to predict net pump performance (ejection fraction). Model predictions showed good agreement with experimental data. Thus, pressure-volume relations can be used to separately quantitate simultaneous changes in ventricular and vascular loading properties in vivo produced by pharmacologic agents with complex actions. Use of this approach in drug testing in humans should simplify data interpretation regarding mechanisms of action in specific clinical settings.

Determinants of end-systolic pressure-volume relations during acute regional ischemia in situ

The influence of extent and location of regional ischemia, baseline left ventricular systolic function, and autonomic reflexes on in situ left ventricular end-systolic pressure-volume relations (ESPVRs) during coronary occlusion were studied in 13 open-chest dogs. Circumflex or left anterior descending arteries were randomly occluded (at proximal or distal sites) for 3 minutes in reflex-blocked (n = 6, hexamethonium/vagotomy) and unblocked (n = 7) animals. Pressure-volume data were obtained by the conductance-catheter technique, with ESPVRs determined by transient inferior vena caval occlusion. Ischemic zone size was estimated for each occlusion by radiolabeled microspheres. The relative influence of each variable on ESPVR change with ischemia was determined by multiple regression analysis. As in previous studies, regional ischemia displaced ESPVRs to the right by an amount that varied directly with ischemic bed size (y = +0.48x, r = 0.76, p less than 0.001). However, in contrast to previous data, coronary occlusion also reduced the ESPVR slope (end-systolic elastance, Ees) in the majority of cases. The extent of slope change was primarily dependent on the baseline elastance (Eesbase), such that the higher the initial elastance, the larger its subsequent reduction for any amount of ischemia (delta Ees = -0.78Eesbase, r = 0.94, p less than 0.001). Active reflexes added an offset constant to this relation (+3.15 mm Hg/ml, p less than 0.001). In addition, Ees fell slightly more with larger ischemic regions. Thus, although previous studies have reported primarily rightward parallel shifts in ESPVR with regional ischemia, the present data also demonstrate that the slope of the relation is often reduced. Greater baseline elastances typical of in situ, as opposed to isolated, ventricles probably explain the differences in apparent responses.