Effect of baseline or changes in adrenergic activity on clinical outcomes in the beta-blocker evaluation of survival trial

BACKGROUND

Adrenergic activation is thought to be an important determinant of outcome in subjects with chronic heart failure (CHF), but baseline or serial changes in adrenergic activity have not been previously investigated in a large patient sample treated with a powerful antiadrenergic agent.

METHODS AND RESULTS

Systemic venous norepinephrine was measured at baseline, 3 months, and 12 months in the beta-Blocker Evaluation of Survival Trial (BEST), which compared placebo treatment with the beta-blocker/sympatholytic agent bucindolol. Baseline norepinephrine level was associated with a progressive increase in rates of death or death plus CHF hospitalization that was independent of treatment group. On multivariate analysis, baseline norepinephrine was also a highly significant (P<0.001) independent predictor of death. In contrast, the relation of the change in norepinephrine at 3 months to subsequent clinical outcomes was complex and treatment group-dependent. In the placebo-treated group but not in the bucindolol-treated group, marked norepinephrine increase at 3 months was associated with increased subsequent risks of death or death plus CHF hospitalization. In the bucindolol-treated group but not in the placebo-treated group, the 1st quartile of marked norepinephrine reduction was associated with an increased mortality risk. A likelihood-based method indicated that 18% of the bucindolol group but only 1% of the placebo group were at an increased risk for death related to marked reduction in norepinephrine at 3 months.

CONCLUSIONS

In BEST, a subset of patients treated with bucindolol had an increased risk of death as the result of sympatholysis, which compromised the efficacy of this third-generation beta-blocker.

A randomized trial of the low-molecular-weight heparin certoparin to prevent restenosis following coronary angioplasty

OBJECTIVES

The objectives of this study were to evaluate the effectiveness and safety of the low-molecular-weight heparin (LMWH) certoparin in preventing restenosis following balloon coronary angioplasty.

BACKGROUND

Restenosis following coronary angioplasty continues to limit the long-term efficacy of this procedure. Animal studies have indicated a potential role for LMWH in reducing restenosis by limiting smooth muscle proliferation.

METHODS

This study tested the effects of certoparin, self-administered for 3 months, in reducing restenosis following balloon coronary angioplasty. One hundred and eighteen patients with 158 lesions treated with angioplasty were enrolled in this randomized, placebo-controlled trial. One hundred and two patients completed the study. The endpoint was relative loss measured with quantitative coronary angiography.

RESULTS

The relative loss for placebo was 0.19 +/- 0.23 compared to 0.14 +/- 0.21 for LMWH (p = NS). The minimum lumen diameter (MLD) was 1.47 +/- 0.66 for placebo and 1.40 +/- 0.57 for the LMWH (p = NS). There was a reduction (31% for LMWH; 49% for placebo PSDP) in the percent of patients having binary restenosis (MLD < 50% of reference diameter). At the end of the study 77% of the placebo patients and 76% of the LMWH group were asymptomatic (p = NS). There was a low rate of bleeding complications and these were minor. Bone density scans showed that there was no significant occurrence of osteoporosis with 3 months of LMWH.

CONCLUSIONS

Administration of certoparin for 3 months is safe, but appears ineffective in reducing post-PTCA restenosis.

"Stunning" of the left atrium after spontaneous conversion of atrial fibrillation to sinus rhythm: demonstration by transesophageal Doppler techniques in a canine model

OBJECTIVES

This study compared left atrial and left atrial appendage contraction velocities in sinus rhythm before and after a brief period of atrial fibrillation in a canine model.

BACKGROUND

In patients, left atrial appendage contraction velocities measured during sinus rhythm after cardioversion from atrial fibrillation are depressed relative to left atrial appendage emptying velocities measured during atrial fibrillation, suggesting that the left atrial appendage is mechanically "stunned."

METHODS

This phenomenon was studied in a canine model of acute (60 min) pacing-induced atrial fibrillation followed by spontaneous reversion to sinus rhythm using epicardial and transesophageal pulsed wave Doppler. Unique features of the model include: 1) comparison of left atrial function postconversion to baseline sinus rhythm rather than to measurements during atrial fibrillation, 2) control of the duration of atrial fibrillation and 3) elimination of the extraneous influences of direct current shock and antiarrhythmic agents, which may independently depress left atrial function.

RESULTS

Hemodynamic conditions (heart rate, mean arterial pressure, cardiac output, mean pulmonary artery pressure, mean right atrial pressure and mean left atrial pressure) at baseline, during 60 min of atrial fibrillation and after reversion to sinus rhythm were constant throughout the study period. Peak left atrial contraction velocities (measured from the transmitral flow velocity profile) were significantly (p < 0.02) reduced to 64+/-22% of baseline values upon spontaneous conversion of atrial fibrillation to sinus rhythm and recovered to basal values by 20 min after resumption of sinus rhythm. Peak left atrial appendage contraction velocities were significantly (p < 0.001) reduced to 49+/-24% of baseline values upon spontaneous conversion of atrial fibrillation to sinus rhythm and recovered to basal values by 40 min after reversion to sinus rhythm.

CONCLUSIONS

Even brief (60 min) periods of atrial fibrillation in normal canine hearts result in marked depression of global left atrial systolic function and regional left atrial (left atrial appendage) systolic function upon resumption of sinus rhythm. This "mechanical stunning" of left atrial systolic function appears to be more profound and of longer duration for the left atrial appendage compared with the left atrium as a whole, which may predispose the appendage to blood stasis and thrombus formation. Chronic models of atrial fibrillation need to be developed to examine the impact of longer periods of atrial fibrillation upon the magnitude and duration of postconversion left atrial "stunning."

Assessment of outcome of bifurcation lesions and non-bifurcation lesions treated in the CAVEAT trial. CAVEAT investigator group

Registry data suggests that bifurcation lesions are associated with reduced success during percutaneous revascularization. We studied 1012 CAVEAT patients to compare procedural outcomes in patients with and without bifurcation lesions whose target vessel was treated with either atherectomy or angioplasty. Bifurcation lesions have increased angiographic complexity and interventions on them are associated with lower acute procedural success rates compared to non-bifurcation lesions. Subgroup analysis suggests that atherectomy treatment of bifurcation lesions improves acute procedural success rates and lowers restenosis rates compared to angioplasty treatment of bifurcation lesions but atherectomy of bifurcation lesions is associated with higher acute complication rates than angioplasty of bifurcation lesions.

Effect of acute pericardial tamponade on the relative contributions of systolic and diastolic pulmonary venous return: a transesophageal pulsed Doppler study

The effect of acute pericardial tamponade on pulmonary venous return was assessed by transesophageal pulsed Doppler echocardiography. In 14 open-chest anesthetized dogs peak pulmonary venous flow velocities in systole (VJ) and in diastole (VK) were measured during apnea and atrial pacing while acute tamponade was induced by intrapericardial instillation of 0.9% sodium chloride solution. Before intravascular volume expansion, induction of acute tamponade resulted in a significant decline in VK (43 +/- 17 to 19 +/- 8 cm/sec; p < 0.05) but no change in VJ or the ratio VJ/VK. After intravascular volume expansion, induction of acute tamponade resulted in significant reductions in VJ (43 +/- 9 to 29 +/- 10 cm/sec; p < 0.001) and VK (37 +/- 19 to 15 +/- 11 cm/sec; p < 0.001). The effect was disproportionately greater on VK, however, resulting in a significant increase in VJ/VK (1.51 +/- 0.84 to 2.58 +/- 1.41; p < 0.001). The disproportionate effect of acute tamponade on VK suggests that increased pericardial pressure directly constrains diastolic filling of the left atrium as a conduit to the left ventricle and that it does not decrease the systolic and diastolic phases of pulmonary venous return uniformly. Intravascular volume expansion increases cardiac output before acute tamponade, but during acute tamponade it amplifies the disproportionate impact of increased pericardial pressure on left ventricular diastolic filling as the left ventricle is constrained within the fluid-filled pericardial sac.

Effects of contrast media on coronary hemodynamics and myocardial metabolism

RATIONALE AND OBJECTIVES

This study was designed to compare the effects of ionic contrast medium (CM), Renografin-76 (R76), and nonionic CM, Omnipaque-350 (OM350), on coronary hemodynamics and myocardial metabolism.

METHODS

In 10 open-chest, atrial-paced dogs, 4 mL of R76 and OM350 were injected into the left anterior descending coronary artery. Coronary blood flow (CBF), myocardial oxygen consumption (MVO2), lactate extraction (LE), left ventricular (LV) dp/dt, and aortic systolic pressure (AOP) were measured.

RESULTS

The maximal CBF changes caused by OM350 and R76 were 23.7 +/- 3.3 mL/minute and 18.3 +/- 3.3 mL/minute (NS), respectively. OM350 produced an increase in LV dp/dt by 378 +/- 85 mm Hg/second, which was different from -244 +/- 65 mm Hg/second by R76 (P < .05). The changes in MVO2 and LE after OM350 injection were 2.6 +/- 0.6 mL/minute and 10.2 +/- 5 microM/minute, respectively; those were different from -0.1 +/- 0.4 mL/minute, and -7.7 +/- 5.1 microM/minute after R76 injection (P < .05).

CONCLUSION

Although both agents increased CBF, they appeared to act by different mechanisms. That a direct coronary vasodilator effect is the main action of R76 on coronary vascular response is suggested by decreasing myocardial contractility and oxygen consumption. However, OM350, by enhancing both parameters, may augment CBF at least in part by autoregulation.

Impairment of myocardial vascular responsiveness after transient myocardial ischemia and reperfusion

Coronary vascular responses after brief periods of myocardial ischemia are impaired. Whereas some studies suggest that the ischemic insult selectively depresses endothelium-dependent vasodilator mechanisms, other studies indicate that even responses to direct vascular smooth-muscle relaxants such as adenosine may be decreased. This study was undertaken to measure regional myocardial blood flow (RMBF) responses to adenosine (a direct coronary vasodilator) and serotonin (an indirect, endothelium-dependent vasodilator) in myocardium subjected to regional ischemia followed by reperfusion. Temporary regional ischemia was achieved by 20 minutes of occlusion of the left anterior descending coronary artery (LAD) followed by 20 minutes of reflow in 10 open-chest anesthetized dogs. In the left circumflex coronary artery (LCX) territory, which served as a nonischemic control, RMBF (measured with radioactive microspheres) increased significantly in response to left atrial infusions of adenosine (1.29 +/- 0.27 to 3.89 +/- 3.89 +/- 2.15 ml/min/gm; p < 0.001) and serotonin (1.29 +/- 0.27 to 3.29 +/- 1.49 ml/min/gm; p < 0.001) and the percent reduction in coronary vascular resistance (% delta CVR) was comparable for these two pharmacologic probes (65% +/- 26% vs 62% +/- 19%; difference not significant [NS]). In contrast, in the myocardium supplied by the LAD, which was subjected to ischemia followed by reperfusion, the augmentation of RMBF by adenosine (1.07 +/- 0.29 to 1.82 +/- 1.35 ml/min/gm; p < 0.001) and serotonin (1.07 +/- 0.29 to 2.37 +/- 1.21 ml/min/gm; p < 0.001) was blunted.(ABSTRACT TRUNCATED AT 250 WORDS)

Restenosis presented with unstable angina and myocardial infarction: one explanation for late cardiac events following directional coronary atherectomy

Three cases of restenosis after directional coronary atherectomy (DCA) presented with unstable angina and then myocardial infarction. Two of them were complicated with malignant ventricular dysrhythmia. A total or subtotal thrombotic occlusion at the DCA site was shown. This fulminating course of restenosis could partially explain the higher late cardiac morbidity and mortality after DCA than after percutaneous transluminal balloon angioplasty.

Alterations in transmitral flow dynamics in patients with early mitral valve closure and aortic regurgitation

Ten patients with severe aortic regurgitation (AR) and early diastolic mitral closure demonstrated by M-mode echocardiography (group I) were compared to 10 age-matched patients with severe AR and normal timing of mitral closure to quantify the accompanying alterations in transmitral flow dynamics assessed by pulsed Doppler echocardiography. Transmitral filling period expressed as a fraction of the time available for diastolic filling was significantly shortened in group I patients relative to group II patients (0.50 +/- 0.10 vs 1.04 +/- 0.09, p < 0.001) because early mitral closure truncated transmitral filling and obliterated the atrial contribution to left ventricular filling. The rapid diastolic filling period normalized for the time available for diastolic filling was also shortened for group I patients relative to group II patients (0.49 +/- 0.11 vs 0.64 +/- 0.19; p < 0.05). Early mitral closure in group I patients was functionally incomplete because 9 of the 10 patients had diastolic mitral regurgitation, which was not detected in any patients in group II (p < 0.001). Thus the group I patients with early mitral closure and severe aortic regurgitation had truncated transmitral inflow and diastolic mitral regurgitation. These patients had higher pulmonary capillary wedge pressures (32 +/- 6 vs 11 +/- 9 mm Hg; p < 0.001) and more severe functional limitation (p < 0.001) than group II patients.

Acute procedural results in the treatment of 30 coronary artery bifurcation lesions with a double-wire atherectomy technique for side-branch protection

Percutaneous treatment of bifurcation lesions has been consistently shown to be associated with lower acute success rates, higher initial complication rates, and an increased rate of restenosis when compared with findings in nonbifurcation lesions. Recent analysis of data from a CAVEAT subgroup suggests that directional atherectomy of bifurcation lesions can improve initial success rates and lower restenosis rates but at the cost of high complication rates. Reports from several angioplasty series document improved success rates and lower complication rates with the use of a two-wire technique to protect side branches when treating bifurcation lesions. Our experience with a two-wire atherectomy technique that uses a nitinol wire to protect important side branches is presented.

The fracture, dislodgement and retrieval of a probe III balloon-on-a-wire catheter

The fracture and dislodgement of an angioplasty device within the coronary arteries is a rare but increasingly noted complication. If the fragment of angioplasty balloon or guidewire is dislodged in a proximal and patent coronary artery, the likelihood of acute embolization which could lead to an acute coronary thrombus and/or myocardial infarction exists. Therefore, the immediate removal of the broken piece of the angioplasty catheter is imperative. A case of unusual fracture and dislodgement of a Probe III Balloon-on-A-Wire catheter and retrieval of the broken piece is reported.

Effect of enalapril, hydralazine plus isosorbide dinitrate, and prazosin on hospitalization in patients with chronic congestive heart failure. The V-HeFT VA Cooperative Studies Group

BACKGROUND

Hospitalization of persons with congestive heart failure for recurrent heart failure or other complications is common.

METHODS AND RESULTS

Male patients aged 18-75 with chronic heart failure were randomized in two sequential trials designed to study the efficacy of vasodilator therapy. Patients were evaluated every 3 months, and information regarding hospitalizations between visits was obtained from the patient, his family, and/or hospital records. Hospitalization data also were obtained for patients who had died between scheduled clinic visits. Hospitalizations were not recorded if a patient died during transit to the hospital or in the hospital emergency department before admission. In Vasodilator-Heart Failure Trial (V-HeFT) I, no significant difference in number of patients hospitalized or number of hospitalizations was noted among the treatment groups, although there was a trend for fewer and delayed cardiac hospitalizations in the hydralazine plus isosorbide dinitrate arm in which the survival was greater. In V-HeFT II, no difference in hospitalizations was apparent between the enalapril and hydralazine plus isosorbide dinitrate arms. Univariate predictors of hospitalization for all causes were reduced peak oxygen consumption (VO2) during exercise (p < 0.0001), reduced exercise duration (p < 0.0001), increased cardiothoracic ratio on chest radiograph (p < 0.0001), increased age (p < 0.03), and use of antiarrhythmic drugs (p < 0.013), whereas multivariate predictors were reduced peak VO2 (p < 0.0001), use of antiarrhythmic drugs (p < 0.015), and increased cardiothoracic ratio (p < 0.03). Univariate predictors of hospitalization for heart failure were peak VO2 (p < 0.0001), LVEF (p < 0.0001), reduced exercise duration (p < 0.0001), elevated cardiothoracic ratio (p < 0.0001), and elevated plasma norepinephrine (p < 0.0001). Multivariate predictors were exercise duration (p < 0.0001), LVEF (p < 0.04), elevated cardiothoracic ratio (p < 0.03), plasma norepinephrine (p < 0.0005), and coronary artery disease (p < 0.02). Time to first hospitalization, cause specific or overall, was considerably shorter for patients with baseline peak VO2 < 10 mL.kg-1 x min-1 compared with those with peak VO2 > 15 mL.kg-1 x min-1.

CONCLUSIONS

Despite better survival in patients randomized to hydralazine plus isosorbide dinitrate compared with placebo and better survival in patients randomized to enalapril compared with hydralazine plus isosorbide dinitrate, no significant differences between the treatment groups were apparent in the incidence of hospitalization or time to first hospitalization for congestive heart failure, for cardiac reasons other than congestive heart failure, or for other causes. V-HeFT I and V-HeFT II data demonstrate no treatment effect on hospitalization, perhaps reflecting in part the effectiveness of the Veterans Affairs special heart failure clinics in dealing with worsening heart failure on an outpatient basis. Identification of predictors of hospitalization were similar in both studies.

Regional changes in blood flow, extracellular potassium and conduction during myocardial ischemia and reperfusion

OBJECTIVES

We postulated that ventricular arrhythmias may arise from the heterogeneous washout of ischemic metabolites. Our objective was to investigate the distribution of extracellular potassium concentration ([K+]o) during myocardial ischemia and reperfusion and to correlate this distribution with regional differences in myocardial blood flow.

BACKGROUND

Our previous study showed that reperfusion after a brief period of ischemia resulted in heterogeneous reflow of the ischemic myocardium.

METHODS

The changes in regional myocardial blood flow, midmyocardial [K+]o and electrogram duration were quantitated in 14 dogs undergoing 20 min of left anterior descending coronary artery occlusion and 1 min of reperfusion. Regional myocardial blood flow was measured by using 15-microns radioactive microspheres in 1- to 1.5-g full thickness myocardial samples. The [K+]o was measured with intramyocardial K(+)-sensitive electrodes.

RESULTS

During coronary occlusion, the ischemic zone exhibited a reduction in regional blood flow to 0.13 +/- 0.06 ml/g per min and increases in [K+]o to 9.3 +/- 2.6 mmol/liter and electrogram duration to 131.8 +/- 38.6% of control. Heterogeneous reduction in regional blood flow at various sites in the ischemic zone had fair correlations with variable increases in [K+]o (r = -0.70) and electrogram duration (r = -0.75). During min 1 of reperfusion, regional blood flow ranged from two to more than seven times baseline, resulting in a disorganized spatial distribution of perfusion with islands of high and low blood flows. Associated with the heterogeneous early reperfusion regional myocardial blood flow, [K+]o and electrogram duration changed at different rates toward normal. Whereas correlation between regional blood flow and [K+]o or standardized electrogram duration was fair during ischemia, this correlation was poor during early reperfusion.

CONCLUSIONS

Spatial heterogeneity in regional myocardial blood flow during myocardial ischemia and early reperfusion is associated with heterogeneity in [K+]o and electrophysiologic characteristics, which in turn may play an important role in the genesis of arrhythmias arising from the ischemic and reperfused myocardium.

New approach to management of intraaortic balloon pumps in patients with peripheral vascular disease: case reports of four patients requiring urgent IABP insertion

Four selected cases of emergent IABP insertion in PV patients are presented. After angiographic documentation of critical iliac stenosis, conservative peripheral angioplasty was performed prior to IABP insertion. No patient experienced a peripheral ischemic event associated with IABP use.

Effects of intracoronary administration of contrast media on myocardial high-energy phosphate. A comparison of sodium meglumine diatrizoate and iohexol

Myocardial ATP, ADP, and AMP were measured from cardiac biopsy in 11 dogs after intracoronary injection of 6 mL of sodium-meglumine diatrizoate (SMD), iohexol (IOH), or 0.9% sodium chloride (NaCl), and in three of the dogs at baseline before any injection. The ATP at baseline and after SMD, IOH, and 0.9% NaCl were 5.39 +/- 0.41, 3.72 +/- 0.70, 5.52 +/- 0.82, and 5.44 +/- 1.40 mumol/g wet weight, respectively. There were significant differences between SMD and IOH (P less than .02), and between SMD and 0.9% NaCl (P less than .05). The energy charge of SMD was 0.82 +/- 0.08, which differed from 0.89 +/- 0.02 for NaCl or 0.9 +/- 0.05 for baseline (P less than .05), but not from 0.85 +/- 0.04 for IOH. In conclusion, diatrizoate caused significant depletions in ATP stores in comparison with iohexol, but there was no significant difference with respect to energy charge. Nonionic contrast media would be preferable for coronary arteriography in patients whose high-energy stores might be depleted from severe ischemia.

Effects of intracoronary administration of contrast media on coronary hemodynamics in a canine post ischemic reperfusion model

Hemodynamic changes due to intracoronary injections of nonionic contrast medium Omnipaque-350 (OM), ionic dimer Hexabrix (HB), and ionic contrast medium Renografin-76 (R76) were compared at baseline and during reperfusion after a 30-minute left anterior descending coronary artery (LAD) occlusion. In 11 open chest, anesthetized, and atrially paced dogs, 4 ml of either OM, HB, R76, or 0.9% NaCl were injected into the carotid-LAD bypass system. Coronary blood flow (CBF) and coronary vascular resistance (CVR) were measured before, during and after the intracoronary injection. The maximal hyperemic change (in percentage) from the preinjection value of CBF and CVR were calculated. The results at baseline and during reperfusion for CBF were: 104 +/- 14% vs. 85 +/- 10% for OM (NS); 76 +/- 11% vs. 39 +/- 9% for R76 (p less than 0.05); 57 +/- 8% vs. 33 +/- 5% for HB (P less than 0.05); and 30 +/- 7% vs. 9 +/- 4% for 0.9% NaCl (p less than 0.05). Consequently, the hyperemic changes of CVR at baseline and during reperfusion were: -49 +/- 3 vs. -42 +/- 4% for OM (NS); -44 +/- 3% vs. -24 +/- 6% for R76 (p less than 0.01); -36 +/- 3% vs. -24 +/- 4% for HB (p less than 0.05); and -18 +/- 4% vs. -7 +/- 3% for 0.9% NaCl (p less than 0.05). Thus, ischemia and reperfusion significantly dampened the coronary hemodynamic and vascular response to R76, HB, and 0.9% NaCl but not to OM. The preserved coronary vascular reserve with high flow in this canine post-ischemic reperfusion model may explain the advantage of nonionic over ionic contrast media used in emergency coronary angiography following thrombolysis.

The effect of sodium on hemodynamic changes during coronary angiography with nonionic contrast media

To investigate the effect of sodium on cardiac hemodynamics, sodium chloride was added to nonionic contrast media to a 0.9% concentration and was compared with the standard media iohexol, iopamidol, and ioversol. Left coronary angiography was performed in 10 closed-chest, atrial-paced dogs with 10 ml injections of each preparation in a randomized and blinded fashion. The maximum changes in left ventricular systolic pressure, mean aortic pressure, left ventricular and diastolic pressure, and maximal rise of left ventricular pressure were measured. The left ventricular systolic pressure and mean aortic pressure decreased by 17 +/- 7 mm Hg and by 12 +/- 5 mm Hg with iohexol plus 0.9% NaCl, but only by 5 +/- 4 mm Hg and by 4 +/- 3 mm Hg with iohexol alone (p less than 0.001). The left ventricular and end diastolic pressure increased by 2.2 +/- 0.6 mm Hg with iohexol plus 0.9% NaCl, but did not change with iohexol alone (p less than 0.001). Left ventricular dp/dt decreased by 204 +/- 161 mm Hg/sec with iohexol plus 0.9% NaCl but increased by 392 +/- 122 mm Hg/sec with iohexol alone (p less than 0.001). Similar results were obtained from experiments with iopamidol versus iopamidol plus 0.9% NaCl and ioversol versus ioversol plus 0.9% NaCl. Ioversol plus 5% dextrose or ioversol plus 2.1% choline chloride (isomolar to ioversol plus 0.9% NaCl) produced a significant increase in left ventricular systolic pressure and left ventricular dp/dt (versus ioversol plus 0.9% NaCl, p less than 0.001). Thus, sodium, but not the osmolality or chloride, contributed to the negative inotropic effect of the contrast media.(ABSTRACT TRUNCATED AT 250 WORDS)

Progression of native coronary artery disease at 10 years: insights from a randomized study of medical versus surgical therapy for angina

Repeat coronary angiography was performed in 42 patients 10 years after randomization to medical (n = 21) or surgical (n = 21) therapy for chronic angina. The native coronary arteries were classified into 15 angiographic segments and 3 arterial trunks for analysis of progression of coronary artery disease. The incidence rate of disease progression in coronary segments was 24% and 28% in medically and surgically treated patients, respectively (p = NS). Grafted segments showed a 38% rate of disease progression, which was higher than the 18% rate of for nongrafted segments (p less than 0.001) and the overall rate of 24% for medically treated patients (p less than 0.01). Similarly, 29 (94%) of 31 grafted arteries exhibited disease progression compared with 19 (59%) of 32 nongrafted arteries (p less than 0.01) and 42 (67%) of 63 arteries in medically treated patients (p less than 0.01). In grafted vessels, disease progression occurred more often in arteries proximal (84%) to the anastomosis than in arteries distal (16%) to graft insertion (p less than 0.001). Progression occurred in 46% of proximal segments compared with 23% of distal segments (p less than 0.02). Progression was seen in 23 (55%) of 43 segments with an occluded graft compared with 30 (31%) of 96 segments with a patent graft (p less than 0.02). Ten years after randomization, medically and surgically treated patients showed a comparable rate of disease progression in coronary segments. However, surgical therapy appeared to significantly accelerate atherosclerotic progression in the grafted vessels, especially in the proximal portions. Occluded grafts also correlated with an adverse effect on disease progression.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of cyclosporine in the mouse heterotopic heart transplant model

We refined the mouse ear-heart transplant model developed by Fulmer and coworkers and tested cyclosporine as a sole immunosuppressive agent in this model. Three-week-old CBA mice were used as heart recipients, and unsexed newborn BALB/c mice were used as heart donors. The heart grafts were examined for visible pulsations at 10-fold to 20-fold magnification daily for the first 10 days and every other day thereafter. Graft electrocardiograms were also obtained on the same schedule. Preliminary studies had established that a dose of 15 mg/kg/day was the optimal cyclosporine dose in our model. This dose was administered subcutaneously to each of two treatment groups. Group 2 received this dose for the entire 30-day experimental period. Group 3 received this dose for the first 16 days of the experimental period. Group 1 consisted of allografts receiving no immunosuppression. Group 1 grafts showed evidence of initial successful engraftment by day 7; however, by day 13 none of the grafts remained viable. In group 2, 19 of 23 grafts remained viable for the entire experimental period. In group 3, all of the grafts remained viable until day 17 (after day 16 cyclosporine was discontinued) and rapidly lost evidence of viability thereafter. By day 21, none of the grafts in group 3 remained viable. Survival curves for the three groups as determined by electrocardiogram and visible pulsations were constructed, and the differences between the curves were significant (p = 0.001). The results of this study demonstrate the potential usefulness of the ear-heart transplantation model in screening immunosuppressive agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of ionic and nonionic contrast media on bradyarrhythmia during coronary angiography: a comparison of Renografin-76, Hypaque-76, and Isovue-370

Contrast media occasionally produce bradyarrhythmias defined as a 25% decrease in heart rate and/or developing atrioventricular block during coronary angiography. Twelve left coronary angiographies and seven right coronary angiographies were performed with 10 ml of diatrizoate meglumine and diatrizoate sodium (Renografin-76 [R76] or Hypaque [H76]) or iopamidol (Isovue 370 [ISO]) in a blinded randomized fashion. Heart rate decreased significantly from 135 +/- 5 to 120 +/- 5 beats/min (p less than 0.001) with R76, to 127 +/- 7 beats/min (p less than 0.01) with H76, and to 130 +/- 6 beats/min (p less than 0.05) with ISO in left coronary angiographies; more profound decrease was observed in right coronary angiographies from 134 +/- 4 to 87 +/- 18 beats/min (p less than 0.001) with R76, to 99 +/- 14 beats/min (p less than 0.001) with H76, and to 125 +/- 7 beats/min (p less than 0.01) with ISO. In 12 left coronary angiographies bradyarrhythmia was observed in five cases with R76, two with H76, and none with ISO. In seven right coronary angiographies it occurred in six with R76, three with H76, and none with ISO. The differences in the incidence of bradyarrhythmia between R76 and ISO were significant during left and right coronary angiographies (p less than 0.05 and p less than 0.01, respectively). Thus ionic contrast media produced more marked bradyarrhythmias than nonionic contrast media in coronary angiography, especially R76. Right coronary angiography resulted in more profound bradyarrhythmias than left coronary angiographies. This study suggested that nonionic contrast media (ISO) might be preferable to ionic contrast media (R76 or H76) for coronary arteriography.

The mechanism and significance of ventricularization of intracoronary pressure during coronary angiography

Ventricularization of pressure during coronary angiography has been said to identify the presence of left main coronary artery disease, but the hemodynamic features and the mechanism of this process have not been studied. Twenty consecutive patients with ventricularization were identified prospectively in our laboratory. Four patients had a discrete ostial left main stenosis and 16 patients had stenosis of the entire length of the left main coronary artery. The degree of pressure drop upon cannulation of the diseased left main coronary artery was highly variable; the systolic pressure decreased by 9 to 94 mm Hg, and the diastolic pressure decreased by 6 to 60 mm Hg. The morphology of the ventricularized pressure was distinct. It had a presystolic deflection resembling an a wave. The upstroke of this waveform was slower and the downstroke was steeper than that of the aortic pressure. An identical waveform was observed in dogs after partial occlusion of the left main coronary artery with a balloon-tipped catheter. The waveform of the so-called ventricularized pressure is derived from the aortic pressure, which is altered by its transmission across the left main coronary stenosis. The appearance of ventricularization is an important clue to the presence of left main coronary artery disease.

Constrictive pericarditis after cardiac surgery

Forty-five patients were identified as having constrictive pericarditis after cardiac surgery. The mean patient age was 61 years (range, 40 to 77 years). Twenty-three of 37 patients with adequate clinical information were reported to have had a diagnosis of postpericardiotomy syndrome after the original surgery. The mean interval from original surgery to presentation with constriction was 23.4 months (range, 1 to 204 months). Computerized tomography was helpful in establishing a diagnosis of constriction in 23 of 29 patients (79%). Bypass graft patency was 93% (85 of 91 grafts). Severe pulmonary hypertension (pulmonary artery systolic pressure greater than or equal to 60 mm Hg) was present in nine patients; 8 had coexistent valvular disease (seven cases of mitral valve disease, and aortic valve disease in one). Thirty-seven of the 45 patients underwent pericardial stripping, 28 of whom experienced marked symptomatic improvement. One patient had persistent right heart failure, which was not documented to be secondary to constriction. Four patients had persistent constrictive physiologic conditions. Three of these patients had more extensive pericardial stripping and showed clinical improvement. Four patients (11%) died within 30 days of stripping. Eight patients received medical therapy alone. The decision to treat patients medically was based either on favorable response to medical therapy (five patients), or poor general clinical status.

The potential risk of thrombosis during coronary angiography using nonionic contrast media

The influence of contrast media on coagulation has an important association with thromboembolic complication during coronary angiography. In this study, whole blood was methodically mixed with nonionic contrast medium, Iohexol (IOH), conventional ionic contrast medium, Hypaque-76 (H76), and low osmolar ionic dimer Hexabrix (HB) in vitro. The thrombotic propensity of contrast agents can be evaluated by measuring the clot formation of the mixtures. The experiments were repeated with whole blood after systemic heparinization. In the in vitro study, 5 ml of canine (N = 10) and 3 ml of human (N = 11) whole blood was incubated for 30 min in glass tubes with equal volumes of IOH, H76, HB, and 0.9% NaCl before heparinization. Clot formation with IOH and 0.9% NaCl were seen both in dogs (4.0 +/- 0.7 gm and 5.6 +/- 0.8 gm) and in patients (1.4 +/- 0.9 gm and 2.9 +/- 1.3 gm), whereas no clot was seen with H76 or XB. Following heparinization, no clot was visualized in any mixture of whole blood with contrast media or 0.9% NaCl. Similar results were observed in the catheter-syringe system with canine blood (N = 11) mixed with the contrast agents. Blood clots found in 15 min and 30 min of IOH were 0.07 +/- 0.08 gm and 0.44 +/- 0.20 gm (P less than 0.01) and of NaCl were 0.29 +/- 0.37 gm and 0.69 +/- 0.38 gm (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of contrast media on the conducting system of the heart during coronary angiography. A comparison of Renografin-76 to Hypaque-76

Electrocardiographic changes induced by ionic contrast media can cause complications during coronary angiography. A conduction delay through various parts of the heart is one factor in the genesis of asystole or ventricular fibrillation. Hypaque-76 (H76) and Renografin-76 (R76) are nearly identical ionic contrast media except that R76 binds more calcium than H76 because of the presence of sodium citrate and EDTA in R76. To determine whether the calcium binding additives in ionic contrast media contribute to the cardiac conduction abnormalities, we examined conduction time through the atrioventricular (AV) nodal tissue (via bipolar His bundle electrograms) and through the distal part of the conduction system (recording the QRS complex from the ECG) during coronary angiography. We injected 10 mL of H76 and R76 in 19 closed chest dogs in a blinded, randomized fashion during coronary angiography. The effects of H76 and R76 on heart rate, AH interval, HV interval, V interval and PR interval, and QRS complex duration were recorded. In 14 nonatrial pacing dogs, compared with H76, R76 produced a greater increase in the AV interval (32.9 +/- 6 milliseconds vs 12.4 +/- 2 milliseconds, P less than .01) and the PR interval (29.6 +/- 6 milliseconds vs 11.9 +/- 4 milliseconds, P less than .02). Additionally, the heart rate decreased 13.9 +/- 3.5 beats/minute from control with R76 compared with a decrease of 4.2 +/- 2.6 beats/minute from control with H76 (P less than .05). There was no significant difference between the prolongation of the HV interval and V interval, or QRS complex duration generated by R76 and H76.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of rapid volume expansion on the right and left cardiac filling pressures after coronary artery bypass surgery

Rapid volume expansion is a diagnostic procedure which can reveal typical hemodynamics of pericardial constriction in patients with pericardial disease who have normal hemodynamics in their baseline state. We studied 20 patients with previous coronary artery bypass surgery in order to determine whether this operation results in some degree of pericardial constriction which could be demonstrated by rapid volume expansion. After infusing 1 L of physiologic saline solution over six minutes, the right atrial pressure increased by 5 +/- 2 mm Hg, the right ventricular diastolic pressure by 4 +/- 3 mm Hg, the pulmonary capillary wedge pressure by 7 +/- 3 mm Hg, and the left ventricular diastolic pressure by 7 +/- 4 mm Hg (mean +/- SD). Equalization of the left and right cardiac pressures was not observed, and the normal respiratory variation of the pressures was not altered by rapid volume expansion. Thus, the pericardial manipulation associated with the performance of coronary artery bypass surgery does not commonly result in the development of subclinical pericardial constriction.

Progression of coronary artery disease after percutaneous transluminal coronary angioplasty

Thirty-nine patients underwent coronary arteriography 1 to 20 months (mean 7 months) after percutaneous transluminal coronary angioplasty (PTCA). At the time of the repeat study, 35 patients (90%) had recurrent angina or myocardial infarction, and 4 patients (10%) were asymptomatic. Restenosis, defined as greater than 50% loss of PTCA gained diameter, was found in 19 patients (49%). In addition, 20 patients had new lesions or marked progression of existing lesions (defined as greater than 20% or increasing greater than 20% obstruction in coronary diameter) in the previously normal or mildly diseased coronary segments. The new or progressive lesions occurred both in patients with restenosis at the PTCA site (nine of 19) and in patients without restenosis (11 of 20). New or progressive lesions tended to occur more commonly in the artery on which PTCA was performed (13 of 40) than in the artery that did not have PTCA (10 of 77) (p less than 0.02 by chi 2). In arteries that had PTCA, new or progressive lesions occurred more often in the segment proximal to the angioplasty site (seven of 13 or 54%) than in the peri-PTCA segment (two of 13 or 15%) and in the segments distal to it (four of 13 or 31%), but this observation did not reach statistical significance. No other clinical, angiographic, or PTCA procedure variables affected the occurrence of new or progressive lesions. In patients with recurrent angina or myocardial infarction after PTCA, both restenosis and new or progressive lesions are common. New lesions or marked progression of existing lesions tended to occur in the vessel subjected to PTCA.(ABSTRACT TRUNCATED AT 250 WORDS)

The response of patients with complex ventricular arrhythmias secondary to dilated cardiomyopathy to programmed electrical stimulation

A prospective study was undertaken to assess the response of patients with idiopathic dilated cardiomyopathy to programmed electrical stimulation (PES). Fifteen patients undergoing evaluation of congestive heart failure were studied. All patients underwent cardiac catheterization and coronary angiography as well as endomyocardial biopsy to exclude known causes of heart failure. No patient had a history of syncope or sustained ventricular arrhythmias. All patients were found to have severe left ventricular dysfunction (mean ejection fraction 17%), as well as nonsustained ventricular tachycardia on ambulatory monitoring or exercise testing. A protocol using up to two premature stimuli and burst pacing, from two right ventricular sites, induced up to four repetitive ventricular responses but failed to induce a sustained ventricular arrhythmia in any patient. Patients with dilated cardiomyopathy, advanced ventricular arrhythmias, and depressed left ventricular function respond differently than do patients with coronary artery disease, advanced ventricular arrhythmias, and depressed left ventricular function, to PES. PES appears to have limited value in the evaluation of patients with dilated cardiomyopathy and nonsustained ventricular arrhythmias.

Effect of acute postinfusion lipemia and free fatty acids on myocardial contractility: assessment with radionuclide ventriculography

Equilibrium gated radionuclide ventriculography was used to evaluate the effect of intravenous fat-emulsion overload and excess of free fatty acids (FFA) on left ventricular ejection fraction (LVEF) in 20 patients with and without coronary artery disease (CAD). Fifteen of these patients had normal (greater than 50%) baseline LVEF and 5 had low (less than 50%) baseline LVEF. From 100 to 150 ml of 20% artificial fat emulsion (Liposyn) was infused over 20-25 min. At the end of the infusion, triglyceridemia reached 820 +/- 220 mg% and left ventricular ejection fraction decreased from baseline 62 +/- 19% (mean +/- SD) to 58 +/- 16% (P less than 0.05, paired t-test). After completion of Liposyn infusion, 5,000 U of heparin was administered intravenously and monitoring of LVEF was continued. One and one-half hours following heparin administration, plasma FFA levels reached 3.7 + 2.0 mmol/l and LVEF rose to 69 +/- 19% (P less than 0.001, paired t-test). Our data indicate that acute intravenous fat overload can suppress and high pathophysiologic levels of FFA can increase LVEF. This effect is more uniform and statistically more reliable in patients with normal LVEF. The study failed to demonstrate any significant difference in the effect of this pharmacologic intervention between patients with and without CAD.

The effect of heart transplantation on Cheyne-Stokes respiration associated with congestive heart failure

Cheyne-Stokes respiration occasionally accompanies the terminal stages of congestive heart failure. We describe this association in a patient requiring heart transplantation. The gradual abatement of Cheyne-Stokes respiration after transplantation supports the delayed circulatory time theory as the mechanism for Cheyne-Stokes respiration in these patients.

Effects of indomethacin on coronary hemodynamics, myocardial metabolism and anginal threshold in coronary artery disease

The effects of orally administered indomethacin or placebo on coronary hemodynamics were studied in 23 patients with coronary artery disease. After indomethacin administration the systemic arterial pressure increased by 12 +/- 4% and the myocardial oxygen consumption by 24 +/- 11%. Coronary sinus flow did not change and coronary vascular resistance increased slightly. Oxygen saturation of the arterial blood did not change, but coronary sinus saturation decreased substantially. Hemodynamic values returned to normal 150 minutes after administration of indomethacin. During rapid atrial pacing, coronary sinus flow increased 79 +/- 14% above the rest value when pacing was done before indomethacin administration; only a 56 +/- 12% increase was seen when pacing was repeated after indomethacin. Peak heart rate achieved during atrial pacing, severity of angina and the degree of ST-segment depression were not altered by indomethacin treatment. Orally administered indomethacin has a mild coronary vasoconstrictive effect that does not interfere substantially with the expected increase in myocardial blood flow during rapid atrial pacing. Anginal threshold is not altered by orally administered indomethacin.

Pacemaker malfunction: fact or artifact?

In summary, the present examples illustrate how pacemaker malfunction can be simulated by the sources of artifact produced or detected by the monitoring equipment. This form of pseudopacemaker malfunction remains a common cause of mistaken diagnosis of pacemaker malfunction. A thorough understanding of the examples outlined above should help distinguish true pacemaker malfunction from pseudopacemaker malfunction produced by artifact.

The usefulness of dobutamine in the assessment of the severity of mitral stenosis

Patients with mitral stenosis often require supine exercise in order to increase their heart rate and cardiac output to assess the severity of their valvular obstruction during cardiac catheterization. We substituted dobutamine for exercise in 14 patients with suspected mitral stenosis. The dobutamine infusion was started at 5 micrograms/kg/min and was increased to 10, 15, and 20 micrograms/kg/min every 3 minutes as tolerated. The heart rate increased from 84 +/- 4 to 123 +/- 7 bpm (p less than 0.001), the cardiac index increased from 2.4 +/- 0.2 to 3.4 +/- 0.2 L/min/m2 (p less than 0.001), and the mean pulmonary artery pressure increased from 27 +/- 3 to 30 +/- 2 mm Hg (p less than 0.02). The pulmonary wedge pressure of 19 +/- 2 mm Hg and the mitral valve index of 0.8 +/- 0.1 cm2/m2 remained unchanged, but the left ventricular end-diastolic pressure decreased from 11 +/- 2 to 6 +/- 2 mm Hg (p less than 0.02). The hemodynamic response during the infusion of dobutamine identified a subgroup of patients with more severe mitral stenosis. Thus, the administration of dobutamine is useful in the evaluation of the severity of mitral valve obstruction during catheterization.

Augmentation of cardiac output by external cardiac pacing: pacemaker-induced CPR

Transthoracic cardiac pacing is frequently associated with simultaneous stimulation of skeletal muscle and nerves. We describe a patient in cardiogenic shock and complete heart block in whom the associated vigorous abdominal and chest muscle contractions caused by transthoracic cardiac pacing resulted in a marked augmentation of cardiac output and systemic blood pressure via a "CPR" effect.

The effects of acute hypertriglyceridemia and high levels of free fatty acids on left ventricular function

The effects of acute hypertriglyceridemia and of high levels of free fatty acids on the left ventricular ejection fraction were studied by radionuclide ventriculography in 20 subjects with and without coronary artery disease. An infusion of approximately 125 ml of a 20% fat emulsion over 25 minutes resulted in an increase of plasma triglycerides to the mean of 820 mg/dl and a fall of the left ventricular ejection fraction from the baseline mean of 62% to 58% (p less than 0.05). Ninety minutes after the intravenous administration of 5000 units of heparin, plasma free fatty acids rose to the mean of 4.6 mmol/L and the mean left ventricular ejection fraction increased to 69% (p less than 0.001). The observed changes in blood lipids were not associated with clinical or ECG evidence of myocardial ischemia. We conclude that acute hypertriglyceridemia causes slight depression of left ventricular performance, while high levels of free fatty acids augment it. However, neither hypertriglyceridemia per se nor its rapid conversion to free fatty acids are likely to cause angina in stable patients with coronary artery disease.

The use of programmed electrical stimulation to assess the fibrillatory propensity of ionic and nonionic contrast media

Coronary angiography occasionally results in ventricular fibrillation. To compare the fibrillatory propensity of conventional ionic and nonionic contrast media, we measured QT intervals and performed programmed electrical stimulation during intracoronary injection of Renografin 76 (R76), Hypaque 76 (H76), and iopamidol (IOP) in 16 open chest dogs. In ten dogs the incidence of ventricular fibrillation following induction of a single premature ventricular beat after every fourth atrial paced beat was 19/20 with R76, 8/20 with H76, and 0/20 with IOP (P less than .001). When two premature beats were induced, the incidence of ventricular fibrillation was 20/20 with R76, 19/20 with H76, and 1/20 with IOP (P less than .001). In six additional dogs, the mean prolongation of the QT interval was 170 +/- 20 msec with R76, 105 +/- 14 msec with H76, and 63 +/- 9 msec with IOP (P less than .001). Thus, programmed electrical stimulation readily induces ventricular fibrillation during intracoronary injection of conventional ionic contrast media. The incidence of ventricular fibrillation parallels the amount of QT interval prolongation produced. H76, which lacks EDTA and sodium citrate, is less fibrillatory than R76. However, the nonionic medium IOP appears far less fibrillatory than either R76 or H76.

Acute anterior myocardial infarction complicated by mural thrombus and peripheral thromboembolism despite anticoagulation

A 43-year-old man had transmural anterior wall myocardial infarction complicated by hypotension and anterior-apical aneurysmal formation. Despite continuous anticoagulation with heparin sodium (heparin) and warfarin sodium (coumadin), a large pedunculated left ventricular thrombus was formed. Four hours after uneventful left ventriculography, the patient experienced acute superior mesenteric embolism. An emergency mesenteric embolectomy and then left ventricular aneurysmectomy with clot evacuation were performed to save the bowel and to prevent further embolization.

Ventricular fibrillation during coronary angiography: reduced incidence in man with contrast media lacking calcium binding additives

The intracoronary injection of contrast media during coronary angiography occasionally results in ventricular fibrillation. Experimental studies have implicated the calcium sequestering agents, sodium citrate and EDTA in Renografin 76 (RG76), as contributing to this complication. Angiovist 370 (AV370) is a contrast medium similar to RG76 except that it contains disodium calcium EDTA instead of EDTA and sodium citrate. To determine if contrast media lacking sodium citrate and EDTA will result in a lower incidence of ventricular fibrillation in man, this investigation compared the incidence of contrast media-induced ventricular fibrillation in patients undergoing coronary angiography with RG76 to that with AV370. Group A consisted of 2,500 consecutive patients undergoing coronary angiography with RG76 and group B consisted of 2,000 subsequent consecutive patients in whom AV370 was employed as the contrast medium. There was no significant difference between groups A and B with respect to the volume of contrast media used per patient (153 +/- 49 ml vs 154 +/- 45ml), age (58.4 +/- 10 vs 58.6 +/- 10 years), sex (70% male vs 70% male), ejection fraction (59 +/- 17 vs 60 +/- 20), history of mitral valve disease (5.8% vs 7.1%), history of aortic valve disease (6.7% vs 6.5%), prior coronary artery bypass graft surgery (6.6% vs 7.3%), or extent of coronary artery disease. Fifteen episodes of contrast media-induced ventricular fibrillation occurred in group A (incidence 0.6%) whereas two episodes occurred in group B (incidence 0.1%) (p less than 0.02). Each patient was successfully defibrillated and no adverse sequelae resulted. Thus the present investigation suggests that the incidence of ventricular fibrillation during coronary angiography can be significantly decreased by using contrast media lacking sodium citrate and EDTA.

Ventricular fibrillation during coronary angiography in dogs: the role of calcium-binding additives

Coronary angiography with Renografin 76 (RG76) occasionally results in ventricular fibrillation (VF). Angiovist 370 (AV370) is a contrast medium similar to RG76 except the calcium-sequestering agents, sodium citrate and EDTA in RG76 have been replaced by calcium EDTA. To determine whether these sequestering agents contribute to contrast medium-induced VF, a comparison was made of the effects of intracoronary injections of RG76, AV370, and saline solutions containing sodium citrate and EDTA (CIT/EDTA) and calcium EDTA (CA EDTA) on myocardial conduction, local QT intervals, and incidence of spontaneous and induced VF in 32 dogs. Four milliliters of RG76 produced a 111 +/- 12-ms increase in local QT intervals, compared with a 73 +/- 8-ms increase with AV370 (p less than 0.001). Spontaneous VF occurred in 12 of 16 six-milliliter injections of RG76, compared with 4 of 16 injections of AV370 (p less than 0.02) An early-cycle premature impulse applied after every fourth beat induced VF in 15 of 16 four-milliliter injections of RG76 compared with 5 of 16 injections of AV370 (p less than 0.01). As the premature beat conducted through the left anterior descending region, conduction slowing and fractionation occurred, which was less with AV370 than with RG76. The CIT/EDTA solution produced a greater increase in QT intervals (77 +/- 5 ms) than the CA EDTA solution (29 +/- 3 ms) or 0.9% saline solution alone (28 +/- 2 ms) (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of dobutamine infusion and supine bicycle exercise for radionuclide cardiac stress testing

We have compared the inotropic drug dobutamine to supine bicycle exercise as a means of inducing stress in radionuclide ventriculography studies. Dobutamine has the following properties, making it favorable for widespread usage: 1) ability to be given safely in a peripheral vein, 2) rapid onset, and 3) short duration of action. Each patient underwent supine bicycle progressive resistance testing of 2 minutes per stage followed 30 minutes later by dobutamine administration. Accuracy of diagnosis was 0.93 and sensitivity was 0.89 with dobutamine, while with bicycle the accuracy was 0.93 and sensitivity was 0.94. While not designed to replace supine bicycle testing, incremental infusions of dobutamine appear to be nearly equal in accuracy and sensitivity, providing a satisfactory technique for cardiac evaluation of previously excluded patients.

Thallium scintigraphy during dobutamine infusion: nonexercise-dependent screening test for coronary disease

Exercise thallium scintigraphy has proven to be a sensitive method for detecting coronary artery disease (CAD). However, early redistribution of thallium and inadequate exercise can reduce its sensitivity. In this study, dobutamine was infused in incremental doses (5, 10, 15, and 20 micrograms/kg/min) in 24 patients being evaluated for chest pain. Thallium scintigraphy was completed during the maximum dose of dobutamine tolerated and repeated 4 hours later. Significant CAD was present in 16 patients; the remaining eight had normal coronaries. Exercise ECG was obtained in 23 patients. During dobutamine thallium scintigraphy, reversible perfusion defects occurred in 15 of 16 CAD and in one of eight non-CAD patients, resulting in a sensitivity of 94% and a specificity of 87%. Exercise ECG had a sensitivity of 60% and a specificity of 63%. We conclude that: (1) dobutamine thallium scintigraphy appears to be a sensitive method for detecting significant CAD and provided a more sensitive screening test than exercise ECG; (2) dobutamine thallium scintigraphy is especially useful in patients who cannot exercise; and (3) because imaging occurs during dobutamine infusion, the problem of early redistribution may be mitigated.

Double-blind crossover randomized trial of intravenously administered verapamil. Its use for atrial fibrillation and flutter following open heart surgery

Fourteen patients with onset of atrial fibrillation (11) or flutter (three) and ventricular rate over 120 beats per minute following cardiac surgery were treated with intravenous (IV) doses of verapamil hydrochloride or placebo in a double-blind crossover protocol. Patients with poor left ventricular function, hypotension, atrioventricular block, and taking beta-blockers and disopyramide were excluded. The dosages were 0.075 mg/kg and 0.15 mg/kg given 15 minutes apart, with termination of study on achieving an end point (conversion to sinus rhythm or slowing of ventricular rate to below 100 beats per minute). None reached the end point with placebo but all with verapamil. Baseline ventricular rate was 144 +/- 20 beats per minute, after placebo 143 +/- 16 beats per minute, and after verapamil 89 +/- 7 beats per minute (mean +/- SD). Thus, IV verapamil briefly slows the ventricular rate of atrial tachyarrhythmias following cardiac surgery.

Effects of low-dose dobutamine on coronary hemodynamics, myocardial metabolism, and anginal threshold in patients with coronary artery disease

Fourteen patients with coronary artery disease and normal or near-normal left ventricular function were studied at rest and during atrial pacing until the occurrence of angina (12 patients) before and during infusion of dobutamine (3.80 +/- 0.45 micrograms/kg/min). At rest, during the infusion, three patients developed chest pain, mean ST segment depression increased from 0.02 to 0.08 mV (p less than .001), and myocardial lactate extraction fell from +17.5% to -1.4% (p less than .05). These ischemic changes were associated with significant increases in arterial systolic pressure (134 to 149 mm Hg), heart rate (79 to 91 beats/min), coronary sinus flow (89 to 113 ml/min), and myocardial oxygen consumption (10.8 to 13.5 cc/min). In contrast, during atrial pacing, dobutamine did not reduce the pacing threshold or further increase myocardial oxygen consumption or ST segment changes; however, arterial mean and diastolic pressures were significantly lower with pacing during dobutamine infusion compared with control pacing. In the absence of heart failure, dobutamine in low doses can cause myocardial ischemia in patients with coronary artery disease. The absence of increased ischemia from dobutamine during pacing may reflect reversal of pacing-induced ventricular dysfunction.

Beneficial effects of dopamine combined with intravenous nitroglycerin on hemodynamics in patients with severe left ventricular failure

Hemodynamic effects of dopamine and intravenous nitroglycerin alone, and in combination, were studied in 27 patients with severe left ventricular failure. Dopamine alone increased cardiac index from 1.8 to 2.5 l/min/m2 but also increased wedge pressure from 24 to 30 mm Hg and heart rate from 88 to 101 beats/min. Arterial oxygen saturation fell from 92% to 87% (p less than .001). Nitroglycerin alone had a lesser effect on cardiac index (1.8 to 2.2 l/min/m2) but decreased wedge pressure from 26 to 16 mm Hg and heart rate from 91 to 86 beats/min. Arterial oxygen saturation fell from 91% to 90% (NS). Combined dopamine and nitroglycerin administration resulted in optimal hemodynamics, with cardiac index of 2.9 l/min/m2, wedge pressure of 17 mm Hg, and heart rate of 96 beats/min. Arterial oxygen saturation remained low at 88% in spite of the reduction in left ventricular filling pressure, which probably reflects increased intrapulmonary right-to-left shunting coupled with increased pulmonary blood flow. These results suggest that the combination of dopamine with intravenous nitroglycerin should be considered for patients with severe left ventricular dysfunction who require temporary pharmacologic support.

Effects of oral dipyridamole on coronary dynamics and myocardial metabolism at rest and during pacing-induced angina in patients with coronary artery disease

The effects of oral dipyridamole administration (150 mg) on coronary hemodynamics, myocardial metabolism, and pacing threshold were studied in 10 patients with significant coronary artery disease (CAD). Following dipyridamole through 120 minutes, there was no significant change in resting heart rate, arterial pressure, coronary venous flow, coronary resistance, myocardial lactate extraction, or myocardial oxygen consumption. Rapid atrial pacing performed before and at 60, 90, and 120 minutes after dipyridamole failed to demonstrate any significant reduction in pacing threshold or evidence of increased ischemia after dipyridamole. Blood dipyridamole levels showed variable and slow absorption which probably explains the difference between intravenous and oral dipyridamole on coronary dynamics and myocardial response to pacing.