Impaired left ventricular diastolic filling in patients with coronary artery disease: assessment with radionuclide angiography

To assess left ventricular (LV) diastolic filling at rest in patients with coronary artery disease (CAD), we analyzed high-resolution time-activity curves (10-20 msec/frame) obtained from gated radionuclide angiograms in 231 patients. Peak LV filling rate (PFR), expressed in end-diastolic volumes per second (EDV/sec), was subnormal in CAD patients (1.8 +/- 0.6 [+/- SD] vs normal mean of 3.3 +/- 0.6, p les than 0.001) and time to PFR (TPFR), measured from end-systole to PFR, was prolonged (171 +/- 41 msec vs normal mean of 136 +/- 23 msec, p less than 0.001). These indexes were also abnormal in the 141 patients with normal resting LV ejection fraction (PFR = 2.1 +/- 0.5 EDV/sec; TPFR = 175 +/- 36 msec) and in 123 patients without Q waves on the ECG (PFR = 2.1 +/- 0.5 EDV/sec; TPFR = 168 +/- 38 msec). Abnormal LV filling at rest (PFR less than 2.5 EDV/sec or TPFR greater than 180 msec) was found in 91% of all patients with CAD, 86% of patients with normal resting LV ejection fractions, 85% of patients without Q waves, and 82% of patients with normal resting LV ejection fraction, no resting regional wall motion abnormalities and no Q waves. Thus, LV diastolic filling, evaluated noninvasively by radionuclide angiography, is abnormal in a high percentage of patients with CAD at rest independent of LV systolic function or previous myocardial infarction.

Long-term hemodynamic assessment of the porcine heterograft in the mitral position. Late development of valvular stenosis

We undertook a study of patients who had porcine mitral valves in place for more than 5 years and who had no clinical signs or symptoms suggestive of valve dysfunction. Of the first 54 patients who had porcine valves implanted in the mitral position, 18 were available for catheterization; all had a routine hemodynamic study postoperatively (mean 7 months) for comparison. Mean follow-up was 85 months (range 61-111 months). Compared with the early postoperative data, there was a significant increase in mean mitral valve gradient, from 5.9 +/- 0.7 to 8.6 +/- 0.7 mm Hg (p less than 0.01), and a significant decrease in calculated mitral valve area, from 2.2 +/- 0.2 to 1.7 +/- 0.2 cm2 (p less than 0.01). Moreover, seven patients showed a decrease in valve area greater than 1.0 cm2, five with valves in place for more than 80 months and only two of 11 patients with valves in place for 80 months or less (p less than 0.05). We conclude that there is a significant incidence of hemodynamic deterioration of porcine heterografts in the mitral position for greater than 5 years, even in patients who are clinically stable.

Doxorubicin cardiotoxicity: assessment of late left ventricular dysfunction by radionuclide cineangiography

Radionuclide cineangiography was used to evaluate 32 patients who sustained long-term remission of soft tissue sarcoma after adjuvant therapy with a cumulative doxorubicin dose from 480 to 550 mg/m body surface area. Left ventricular ejection fraction at rest was below normal (less than 45%) in eight of 32 patients. The abnormal response of ejection fraction to exercise identified an additional 12 patients with diminished left ventricular functional reserve. Ejection fraction determined at rest or during exercise did not differ 1 to 9 months) and those studied 30 months (range, 21 to 43 months) after completing doxorubicin treatment. Sequential studies in 13 patients, done 6 to 15 months after initial post-doxorubicin evaluation also showed persistent depression of average ejection fraction at rest and with exercise, with the continued deterioration of left ventricular function in six patients. Left ventricular dysfunction, evident in over half of asymptomatic patients even long after "acceptable" cumulative doses of doxorubicin, may persist for years.

Measurement of ventricular function by ECG gating during atrial fibrillation

The assumptions necessary to perform ECG-gated cardiac studies are seemingly not valid for patients in atrial fibrillation (AF). To evaluate the effect of AF on equilibrium gated scintigraphy, beat-by-beat measurements of left-ventricular function were made on seven subjects in AF (mean heart rate 64 bpm), using a high-efficiency nonimaging detector. The parameters evaluated were ejection fraction (EF), time to end-systole (TES), peak rates of ejection and filling (PER,PFR), and their times of occurrence (TPER,TPFR). By averaging together single-beat values of EF, PER, etc., it was possible to determine the true mean values of these parameters. The single-beat mean values were compared with the corresponding parameters calculated from one ECG-gated time-activity curve (TAC) obtained by superimposing all the single-beat TACs irrespective of their length. For this population with slow heart rates, we find that the values for EF, etc., produced from ECG-gated time-activity curves, are very similar to those obtained from the single-beat data. Thus use of ECG gating at low heart rates may allow reliable estimation of average cardiac function even in subjects with AF.

Lack of effect of aspirin on myocardial infarct size in the dog

Pretreatment with platelet-inhibitory doses of aspirin (3 mg/kg body weight) has been shown to augment epicardial collateral flow by more than 50 percent (p less than 0.05) 4 hours after ligation of the left anterior descending coronary artery in dogs. To determine whether this favorable influence of aspirin is sufficient to decrease the amount of infarcted tissue, either intravenous aspirin, 3 mg/kg (n = 17), or saline solution (n = 17) was administered to dogs 10 minutes before occlusion of the left anterior descending coronary artery. Administration of saline solution or aspirin was repeated every 24 hours. By 72 hours, 5 dogs in each treatment group had died. Survivors were killed at 72 hours. The portion of the left ventricle at risk of infarction was delineated by perfusion of the aortic root with Evans blue and simultaneous perfusion of the distal left anterior descending coronary artery with saline solution under equal physiologic pressures. Slices of the stained heart were incubated with triphenyltetrazolium to identify gross infarct (with histologic confirmation). Total mass of left ventricle, myocardium at risk, and infarct size were measured in each dog. A direct relation was found between the mass at risk and the mass infarcted (r = 0.84, p less than 0.001). Aspirin-treated dogs did not differ from control dogs in percent ventricle at risk (mean +/- standard error 37 +/- 2 versus 40 +/- 2), percent infarct weight/left ventricle (29 +/- 3 versus 31 +/- 2) or percent infarct weight/weight of ventricle at risk (78 +/- 4 versus 77 +/- 3). Thus, despite aspirin's ability to inhibit platelet aggregation and to increase epicardial collateral flow by more than 50 percent, aspirin treatment failed to reduce infarct size in this dog model.

Hypertrophic cardiomyopathy with unusual locations of left ventricular hypertrophy undetectable by M-mode echocardiography. Identification by wide-angle two-dimensional echocardiography

Twenty-one patients without evidence of hypertrophy by M-mode echocardiography were studied by wide-angle two-dimensional echocardiography to determine if they had a form of hypertrophic cardiomyopathy that could not be detected by conventional M-mode echocardiography. Each patient was suspected clinically of having hypertrophic cardiomyopathy because of a distinctly abnormal ECG and either a family history of hypertrophic cardiomyopathy or cardiac symptoms. Patients were 5-49 years old (mean 16 years) and 16 of the 21 had no functional limitation. The most common electrocardiographic abnormalities were deep Q waves, T-wave inversion and right ventricular hypertrophy. Using wide-angle two-dimensional echocardiography to reconstruct the geometry of the left ventricular wall, 16 of the 21 patients (76%) were shown to have prominent but unusually located regions of left ventricular wall hypertrophy. In each instance, the hypertrophy involved regions of the left ventricular wall through which the M-mode ultrasound beam does not usually pass, i.e., posterior ventricular septum (seven patients), anterior or lateral left ventricular free wall (seven patients) and ventricular septum near the apex (two patients). There was no echocardiographic or hemodynamic evidence of left ventricular outflow tract obstruction in any patient. Hence, some patients with hypertrophic cardiomyopathy may have substantial hypertrophy present in unusual locations of the left ventricular wall. Although electrocardiographic abnormalities suggested the presence of myocardial disease, conventional M-mode echocardiography (performed from standard parasternal positions) did not reliably identify such sites of hypertrophy, which were limited to regions of the left ventricle not accessible to the M-mode beam. Only wide-angle two-dimensional echocardiography permits definitive identification of these unusually located regions of cardiac hypertrophy and confirmation of the diagnosis of hypertrophic cardiomyopathy.

Aortic valve replacement without myocardial revascularization in patients with combined aortic valvular and coronary artery disease

To test the hypothesis that coronary artery bypass grafting (CABG) is not routinely required in patients undergoing aortic valve replacement (AVR) who have coexistent coronary artery disease (CAD), we compared the results of operation in 55 consecutive symptomatic patients who had CAD and underwent AVR without CABG with results in another 142 patients without CAD who underwent AVR during the same period, and with published results from other centers in which CABG was used in patients with CAD who underwent AVR. Operative mortality was 4% in patients with CAD and 5% in patients without CAD. Late survival was not significantly different between the two groups when analyzed for the entire population (80% survival at 3 years in CAD patients, 82% for non-CAD patients), or for the subgroup of patients with aortic stenosis, aortic regurgitation or aortic stenosis plus regurgitation. Eight patients with CAD (15%) developed recurrent angina after AVR (mean follow-up 43 months); only three patients (6%) required CABG because of medically refractory angina (12-43 months). Operative mortality, operative infarction (9%), recurrent angina and long-term survival in patients with CAD after AVR were similar to those at other centers after AVR plus CABG. These data suggest that preoperative detection of CAD does not necessitate CABG in all patients at the time of AVR.

Preoperative exercise capacity in symptomatic patients with aortic regurgitation as a predictor of postoperative left ventricular function and long-term prognosis

Forty-five symptomatic patients with aortic regurgitation underwent graded treadmill exercise testing before operation. Twenty-seven patients (group A) could not complete stage I of the National Institutes of Health exercise protocol because of limiting symptoms (exercise duration less than or equal to 22.5 minutes); 18 patients (group B) completed this stage without limiting symptoms (exercise duration > 22.5 minutes). Patients in group A had higher resting pulmonary capillary wedge pressures (mean 19 vs 13 mm Hg, p < 0.05) and left ventricular (LV) end-diastolic pressures (mean 24 vs 16 mm Hg, p < 0.05) than those in group B, but did not differ with respect to LV systolic dimension or fractional shortening by echocardiography or LV ejection fraction at rest or during exercise by radionuclide cineangiography. Among 32 patients with subnormal preoperative LV fractional shortening on echo, nine of 17 in group A and 0 of 15 in group B have died (p < 0.01); seven of the nine deaths were from late congestive heart failure. Group A patients also had less decrease postoperatively in LV diastolic size by echocardiography (mean decrease 8 vs 23 mm, p < 0.001) and less increase postoperatively in LV ejection fraction during exercise by radionuclide cineangiography (mean increase 11% vs 23%, p 0.05) than group B patients. No group A patient and 60% of group B patients had normal exercise ejection fractions postoperatively (p < 0.01). The differences in postoperative mortality and function were not predicted by the differences in preoperative hemodynamics between the two groups. Thus, exercise capacity is imprecise in assessing preoperative LV function in symptomatic patients with aortic regurgitation, but is useful in predicting long-term survival after operation and reversibility of LV dilatation and systolic dysfunction.

Relative effects of aspirin on platelet aggregation and prostaglandin-mediated coronary vasodilatation in the dog

Aspirin, as an inhibitor of platelet aggregation, may be of benefit in ischemic heart disease. However, aspirin blocks not only platelet aggregation but also synthesis of prostacyclin, a vasodilator and platelet deaggregator. The relative sensitivity of prostaglandin-mediated coronary vasodilatation and platelet aggregation to inhibition by aspirin remains uncertain. We therefore investigated the relative dose-response relationship of aspirin on arachidonic acid-induced increments in coronary blood flow and on ADP-induced aggregation of platelets. In 11 open-chest dogs, intracoronary arachidonic acid, 0.1-3.0 mg, produced dose-related increases in coronary blood flow that were inhibited progressively by i.v. aspirin over the dose range 0.3-3.0 mg/kg. Aspirin at 3 mg/kg almost completely obliterated the response to 3 mg of arachidonic acid. Similarly, aspirin doses of 0.3-3.0 mg/kg progressively raised the minimal concentration of ADP necessary for platelet aggregation. The threshold concentration of ADP that produced aggregation of platelets from 10 control dogs ranged from 2.3 x 10(-6) M to 1.2 x 10(-5) M. Aspirin at 3 mg/kg completely inhibited aggregation of platelets from 11 of 12 dogs, even with ADP at 2.3 x 10(-4) M concentration, the maximum tested. Aspirin at 0.1 mg/kg failed to inhibit either ADP-induced platelet aggregation or arachidonic acid-induced increments in coronary blood flow. Thus, the two test systems showed similar sensitivity to inhibition by aspirin with respect to threshold dose and maximal effect. These results show that very low doses of aspirin inhibit arachidonic acid-induced coronary vasodilatation and that aspirin at low doses does not appear to selectively inhibit platelet activity relative to coronary vasodilatation.

Effect of exercise conditioning on plasma high density lipoproteins and other lipoproteins

Epidemiologic studies have demonstrated an inverse correlation between HDL-cholesterol and the incidence of coronary artery disease. Although physically active individuals tend to have higher HDL levels than their sedentary peers, they also have lower body weights. It has yet to be shown that physical activity by itself can raise HDL when other variables such as body weight are maintained constant. We examined the effect of a 6-week exercise conditioning program on 10 young normal subjects who were maintained on a constant composition, iso-weight diet. A training effect was documented by an increase in maximum oxygen consumption from 44 to 49 ml/min/kg and by a fall in heart rate at submaximal exercise from 120 to 109 beats/min. Total plasma cholesterol levels decreased significantly from 156 to 140 mg/dl. However, there was no significant change in plasma triglyceride, VLDL, LDL or HDL-cholesterol levels, although all these values decreased. Thus, under the conditions of this study in which diet and weight were controlled, exercise conditioning did not elevate HDL-cholesterol levels. HDL levels have been shown to be inversely related to body weight. These data are consistent with the concept that exercise conditioning may affect HDL via alterations in body weight.

Beat-by-beat validation of ECG gating

Ejection fraction, normalized peak ejection and filling rates, and the time of occurrence of these events relative to the R-wave were determined in each of 512 consecutive individual cardiac cycles in each of 30 patients using an ultra-high-efficiency nonimaging detector system. For a given patient the 512 measurements of each quantity were averaged and compared with the value of this same quantity as determined from an R-wave-gated left-ventricular (LV) time-activity curve (TAC) derived from the same 512 cycles. We conclude (a) that a small but detectable systematic underestimate occurs in some LV function parameters when they are derived from gated LV TACs; (b) that the magnitude of this underestimate is smaller and less variable for systolic than for diastolic measurements; (c) that the magnitude of the underestimate is not greater than 20% in any single patient for diastolic parameters, nor greater than 8% in any individual patient for systolic parameters, and is substantially less for most patients; and (d) that a small subset of patients may require beat-length windowing if the gated values of diastolic parameters are to fall within these limits. Thus LV function measurements obtained from gated TACs adequately reflect the true average of such values during the measurement interval.

Evaluation of aortic valve replacement in patients with valvular aortic stenosis

Echocardiographic and hemodynamic studies were obtained in 42 consecutive patients undergoing aortic valve replacement for isolated aortic stenosis. Concentric left ventricular (LV) wall thickening, the most common preoperative abnormality, occurred in 95% of patients. LV dilation with reduced fractional shortening was noted in approximately 25% of patients but was severe in only one patient. Six months after operation, LV wall thickness had decreased on average but had not returned to normal and fractional shortening was unchanged. Repeat measurements in 13 patients an average of 37 months after operation were unchanged compared with measurements made 6 months after operation. When patients were subdivided into those with LV dilatation and those without, we found that patients with dilated ventricles preoperatively had a greater decrease in LV internal dimension and mass than those without preoperative dilatation. The patient data also were examined for possible association with mortality. One operative (2%) and five late cardiac (13%) deaths occurred. No preoperative or 6-month postoperative echocardiographic or hemodynamic measurement was strongly associated with these deaths, nor were any late deaths due to congestive heart failure. Compared with preoperative measurements in symptomatic patients who were operated for isolated aortic regurgitation, patients with aortic stenosis had smaller left ventricles with less depression of systolic function, as well as less aortic root and left atrial dilatation. Our data do not support the concept that the aortic valve should be replaced before the onset of symptoms to prevent irreversible LV damage in patients with isolated aortic stenosis.

Observations on the optimum time for operative intervention for aortic regurgitation. I. Evaluation of the results of aortic valve replacement in symptomatic patients

Fifty consecutive patients undergoing aortic valve replacement for isolated aortic regurgitation were studied prospectively by echocardiography, electrocardiography and cardiac catheterization. Good quality echocardiograms were obtained in 49 of the 50 patients. Left ventricular (LV) dilatation was present in all 49 patients. LV systolic function, as assessed by echocardiographic percent fractional shortening, was normal in many patients but was moderately to severely reduced (less than 25%) in 14 patients (29%). Echocardiographic studies 6 months postoperatively revealed significant reductions in LV end-diastolic dimension (73.8 mm vs 58.7 mm; p less than 0.01), and serial echocardiographic studies early and late after operation revealed that the decrease in LV size had occurred by the time of the early study (8-22 days postoperatively), with little additional change thereafter. Operative deaths occurred in three of the 49 patients (6%). Eight of the 49 patients (16%) died of congestive heart failure (CHF) after hospital discharge at times ranging from 5-43 months after operation. Preoperative echocardiographic measurements of the LV end-systolic dimension and percent fractional shortening were strongly associated (p less than 0.01) with these late CHF deaths. Preoperative LV end-systolic dimension greater than 55 mm and fractional shortening less than 25% identified the high-risk group: nine of 13 patients (69%) in this group died either at operation or subsequently from CHF. In contrast, of 32 patients with LV end-systolic dimension less than 55 mm, only one died at operation and one died late from CHF. Thus, the population at high risk of late death from CHF was identified before operation by echocardiography.

Spontaneous gap phenomenon in atrioventricular conduction produced by His bundle extrasystoles

A gap in atrioventricular conduction is a zone within the cardiac cycle during which premature impulses are blocked in the conduction system, while impulses of greater or lesser prematurity are conducted. This has previously been produced only by atrial or ventricular stimulation techniques. This report demonstrates a spontaneous gap produced by His extrasystoles.