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Biomedical subjects

R O Bonow

Publications and source records attributed to R O Bonow.

At least 145 records · Page 8Linked to original sources
PubMed1989

Effect of surgical reduction of left ventricular outflow obstruction on hemodynamics, coronary flow, and myocardial metabolism in hypertrophic cardiomyopathy.

To assess the impact of operative reduction of left ventricular outflow obstruction in hypertrophic cardiomyopathy, measurements of great cardiac vein flow, oxygen and lactate content, left ventricular pressures, and cardiac index were measured at rest and during pacing stress in 20 consecutive patients (13, myotomy-myectomy; six, mitral valve replacement; one, both myotomy-myectomy and mitral valve replacement) who underwent both preoperative and postoperative studies. All had angiographically normal epicardial coronary arteries. Operation resulted in reduction in outflow gradient (64 +/- 38 to 4 +/- 7 mm Hg, p less than 0.001) and in left ventricular systolic pressure (186 +/- 32 to 128 +/- 22 mm Hg, p less than 0.001) and was associated with reduction in great cardiac vein flow (101 +/- 26 to 78 +/- 16 ml/min, p less than 0.001) and oxygen consumption in the anterior left ventricle and septum (11.9 +/- 4.1 to 8.4 +/- 1.9 ml O2/min, p less than 0.001) in the basal state. During rapid atrial pacing, 13 of 20 patients experienced chest pain postoperatively, whereas all 20 developed chest pain during preoperative pacing, with an improvement in pacing anginal threshold (or heart rate 150 if no chest pain was experienced) of 16 +/- 18 beats/min (p less than 0.001). The peak great cardiac vein flow (161 +/- 41 to 131 +/- 45 ml/min, p less than 0.025) and myocardial oxygen consumption (19.4 +/- 6.1 to 14.3 +/- 5.5 ml O2/min, p less than 0.005) during pacing, which correlated directly with the severity of the basal left ventricular gradient (p = 0.011 and p = 0.002, respectively), were also reduced by surgery. Lactate metabolism during pacing changed from net production before surgery to net consumption after operation (-17 +/- 47.6 to 4.4 +/- 29.8 mumol/min, p less than 0.01), with six of 20 patients producing lactate after surgery compared with 13 of 20 before surgery (p = 0.06). The six patients with the highest peak great cardiac vein flow (greater than 175 ml/min) during preoperative pacing had greater symptom and metabolic benefit during pacing after surgery compared with the 14 patients with lower peak coronary flow. Postpacing left ventricular end-diastolic pressure (30 +/- 7 to 23 +/- 7 mm Hg, p less than 0.001) and pulmonary artery wedge pressure (24 +/- 6 to 20 +/- 5, p less than 0.001) were reduced after surgery.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1989

Verapamil prevents silent myocardial perfusion abnormalities during exercise in asymptomatic patients with hypertrophic cardiomyopathy.

Recent studies indicate that reversible 201Tl perfusion defects, compatible with silent myocardial ischemia, commonly develop during exercise in asymptomatic or mildly symptomatic patients with hypertrophic cardiomyopathy (HCM). To determine whether this represents a dynamic process that may be modified favorably by medical therapy, we studied 29 asymptomatic or minimally symptomatic patients with HCM, aged 12-55 years (mean, 28), with exercise 201Tl emission computed tomography under control conditions and again after 1 week of oral verapamil (mean dosage, 453 mg/day). Treadmill time increased slightly during verapamil (21.0 +/- 3.6 to 21.9 +/- 2.7 minutes, p less than 0.005), but peak heart rate-blood pressure product was unchanged (26.3 +/- 6.0 X 10(3) compared with 25.0 +/- 6.4 X 10(3). Two midventricular short-axis images per study were divided into five regions each, and each of these 10 regions was then analyzed on a 0-2 scale by three observers blinded with regard to the patients' therapy. Average regional scores of 1.5 or less were considered to represent perfusion defects, and a change in regional score of 0.5 or more was considered to constitute a significant change. During control studies, 15 patients (52%) developed perfusion defects with exercise (average, 3.7 regions per patient). In 14 of these patients, all perfusion defects completely reversed after 3 hours of rest; one patient had fixed defects. After administration of verapamil, exercise perfusion scores improved in 10 of the 14 patients (71%) with reversible defects; there was overall improvement in 34 of 50 (68%) regions with initially reversible perfusion defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Electrophysiologic abnormalities in patients with hypertrophic cardiomyopathy. A consecutive analysis in 155 patients.

Electrophysiologic studies (EPS) were performed in 155 patients with hypertrophic cardiomyopathy (HCM). Indications for EPS were cardiac arrest in 22 patients, syncope in 55 patients, presyncope in 37 patients, asymptomatic ventricular tachycardia (VT) in 24 patients, palpitations in 10 patients, and a strong family history of sudden cardiac death in seven patients. Thirty-five (23%) patients had significant resting left ventricular outflow tract obstruction. Electrophysiologic abnormalities were present in 126 (81%) patients. A high prevalence of abnormal sinus-node function (66%) and His-Purkinje (HV) conduction (30%) was noted. The most commonly induced supraventricular arrhythmias were atrial reentrant tachycardia and atrial fibrillation (10% and 11% of patients, respectively). Accessory atrioventricular pathways were present in seven (5%) patients. Programmed ventricular stimulation (PVS) induced nonsustained ventricular tachycardia in 22 (14%) patients and sustained ventricular arrhythmia in 66 (43%) patients. Sustained ventricular arrhythmia was polymorphic VT in 48 (73%) patients, monomorphic VT in 16 (24%) patients, and ventricular fibrillation in two (3%) patients. Induction was with two premature stimuli in 19 (29%) patients and three premature stimuli in 47 (71%) patients. Of 17 cardiac arrest survivors with sustained ventricular arrhythmia, 16 (94%) patients required three premature stimuli for arrhythmia induction. Sustained ventricular arrhythmia was induced at a right ventricular site in 51 (77%) patients and at a left ventricular site in 15 (23%) patients. Univariate analysis showed a significant (p less than 0.05) association between inducibility of sustained ventricular arrhythmia and VT on Holter in patients with a history of cardiac arrest or syncope but not in patients with presyncope or asymptomatic patients. Multivariate logistic regression analysis revealed that the following were significantly associated with inducibility of sustained ventricular arrhythmia: clinical presentation (cardiac arrest more than syncope more than presyncope more than asymptomatic patients, p = 0.0002; chronic or inducible atrial fibrillation, p = 0.002; and male gender, p = 0.04). In contrast, there was no clinical correlate of induced nonsustained VT.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1989

Cardiorespiratory effects of immunotherapy with interleukin-2.

The administration of interleukin 2 (IL-2) and lymphokine-activated killer (LAK) cells can mediate the regression of cancer. Treatment with IL-2 is associated with significant cardiorespiratory effects, as well as a leaky capillary syndrome requiring careful fluid management. A mild reversible depression of cardiac function is also associated with IL-2 treatment. All patients treated with recombinant IL-2 alone, with transfer of LAK cells, or with cyclophosphamide between December 1984 and September 1987 (total of 423 treatment courses in 317 total patients) were evaluated as to the development of significant cardiorespiratory toxicity. Of the 423 treatment courses, only 1.8% were associated with severe peripheral edema and only 2.8% and 3.1% respectively, were associated with significant ascites or pleural effusions. Thirty-nine of 423 patients (9.2%) had severe respiratory distress and 27 patients required intubation (6.4%). Cardiovascular effects included tachycardia and hypotension requiring vasopressor administration in 65% and intravenous (IV) fluid administration. Weight gain greater than or equal to 10% of body weight was noted in 32% of the 423 patients. Arrhythmias were primarily supraventricular (9.7%) and responded well to conventional medical treatments. Angina or ischemic changes were noted in 2.6% of patients and myocardial infarction in 1.2%. IL-2 caused peripheral vasodilation, with a significant decrease in peripheral vascular resistance (2,254 +/- 398 v 1,303 +/- 351 dyne.s.cm-5, P less than .0001), and an increase in heart rate (66.2 +/- 10 v 104.3 +/- 9.6 beats/min, P less than .0001). There was also evidence of mild cardiac dysfunction, with a significant decrease in the left ventricular stroke work (LVSW) index (P less than .0001) and ejection fraction (LVEF) (from 58% +/- 10% to 52% +/- 9%, P less than .03). A repeat LVEF performed after 1 to 3 months, had returned to baseline values (60% +/- 10%). A mean 64% increase in the rate of disappearance of radioactive iodine (125I) albumin (P less than .05) consistent with the development of a leaky capillary syndrome was noted. Patients with underlying cardiorespiratory diseases may be at greater risk during IL-2 administration and should not be selected to undergo this treatment.

Adult↗
PubMed1989

Diagnosis of coronary artery disease by radionuclide angiography: effect of combining indices of left ventricular function.

The aim of this study was to determine whether the diagnostic capability of radionuclide angiography (RNA) in detecting coronary artery disease (CAD) might be improved by using several indices of left ventricular (LV) function in concert. Three different models (rest data, exercise data, and rest plus exercise data) were derived by stepwise multivariate discriminant analysis of RNA data in 65 normal volunteers and 111 patients with CAD and normal ejection fraction (EF) at rest. The model with only resting indices yielded a diagnostic capability comparable to the simple measure of EF response to exercise (area under receiver operating characteristic curve = 89% and 91%, respectively). Both the exercise and rest plus exercise models gave better results (area = 94% and 97%, respectively), but only the rest plus the exercise model was better than the EF response alone (p less than 0.001). Thus (a) if resting studies alone are performed, the diagnostic potential of RNA may be improved by combining several indices of resting function; and (b) combined rest and exercise data may improve the sensitivity of RNA in detecting CAD over what could be obtained with the EF response to exercise alone.

Adult↗
PubMed1988

Angina due to coronary microvascular disease in hypertensive patients without left ventricular hypertrophy.

When angina occurs in patients with hypertension, it is usually attributed to coronary artery disease or left ventricular hypertrophy. To determine the contribution of coronary microvascular abnormalities to angina in patients with hypertension, we evaluated hypertensive patients without coronary artery disease or left ventricular hypertrophy by measuring the coronary responses to rapid atrial pacing before and after administration of ergonovine. We compared 12 hypertensive patients who had pacing-induced angina with 13 normotensive subjects without such angina. The two groups had similar coronary flow (in the great cardiac vein) at rest; however, pacing increased coronary flow less in hypertensive patients with angina than in normotensive subjects (48 vs. 83 percent; P = 0.05). In the hypertensive patients with angina, pacing after ergonovine increased coronary flow by only 32 percent (as compared with 48 percent before ergonovine; P less than 0.05) and decreased coronary resistance by 15 percent (as compared with 28 percent before ergonovine; P less than 0.05), indicating the presence of ergonovine-induced vasoconstriction. In normotensive subjects, in contrast, cardiac pacing after ergonovine increased coronary flow by 112 percent (P less than 0.001), and its effect on coronary resistance was not different from that of pacing before ergonovine. The hypertensive patients with angina had a significant increase in myocardial oxygen extraction during pacing after ergonovine and less of an increase in myocardial lactate consumption - a response consistent with the presence of myocardial ischemia. Thus, angina in hypertensive patients without epicardial coronary disease may be caused by myocardial ischemia, which appears to be due to an abnormally elevated resistance of the coronary microvasculature.

Angina Pectoris↗
PubMed1988

The effect of coronary artery bypass grafting on left ventricular systolic function at rest: evidence for preoperative subclinical myocardial ischemia.

Successful coronary artery bypass grafting (CABG) improves exercise-induced left ventricular (LV) dysfunction in patients with coronary artery disease (CAD), but its potential for improving resting LV function remains controversial. To assess the influence of CABG on LV function at rest, 31 CAD patients without previous myocardial infarction were studied before and 6 months after CABG by radionuclide angiography after all cardiac medicines were withdrawn. No patient had angina or ischemic electrocardiographic changes at rest. In 27 patients with patent bypass grafts, CABG significantly increased LV ejection fraction during exercise (47 +/- 11% before to 63 +/- 9% after operation, p less than 0.001), indicating reduction in exercise-induced LV ischemia. Moreover, LV ejection fraction at rest also increased (55 +/- 9 to 60 +/- 8%, p less than 0.001), with 20 of 27 patients manifesting an increase compared with preoperative values. Eleven of these 20 patients had apparently normal LV function at rest (ejection fraction and regional wall motion) before CABG. LV regional ejection fraction was computed by dividing the LV region of interest into 20 sectors. Regional analysis indicated that improved ejection fraction at rest after CABG occurred in regions developing ischemia during exercise before CABG. In 4 patients with occluded grafts, the ejection fraction at rest was unchanged by CABG globally (59 +/- 8 to 58 +/- 9%, difference not significant) and regionally. Thus, LV global and regional function at rest improved after successful CABG, even in patients with normal global LV ejection fraction and no visually detectable wall motion abnormality before surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Relation between serum nifedipine concentration and hemodynamic effects in nonobstructive hypertrophic cardiomyopathy.

The relation between nifedipine concentration and hemodynamic effects after sublingual administration of 10 or 20 mg was examined in 13 patients with nonobstructive hypertrophic cardiomyopathy (HC). Serum nifedipine concentrations were determined by gas chromatography and were not related to dose. Peripheral vascular resistance decreased as a function of nifedipine concentration (r = -0.63, p less than 0.001); this was associated with a concentration-related increase in heart rate (r = 0.56, p less than 0.001) and in cardiac index (r = 0.50, p less than 0.001). However, evidence for a pure vasodilator effect of nifedipine was inconsistent, in that the change in stroke volume index with nifedipine was not significant. Although stroke volume index increased at nifedipine concentrations between 60 and 120 ng/ml (38 +/- 6 to 42 +/- 4 ml/m2, p less than 0.01), it decreased at concentrations greater than 120 ng/ml (40 +/- 3 to 38 +/- 4 ml/m2, p less than 0.01). Moreover, pulmonary artery wedge pressure increased at nifedipine concentrations greater than 120 ng/ml (11 +/- 2 to 16 +/- 4 mm Hg, p less than 0.001), suggesting either depressed left ventricular (LV) systolic function or reduced LV filling. To investigate these possible mechanisms, LV systolic and diastolic function was studied during catheterization with a nonimaging scintillation probe in 6 of the 13 patients. In these subjects, heart rate was held constant by atrial pacing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Effects of aging on asynchronous left ventricular regional function and global ventricular filling in normal human subjects.

In many patients with coronary artery disease or hypertrophic cardiomyopathy, reduced left ventricular rapid diastolic filling is related to asynchronous left ventricular regional diastolic function. Because left ventricular filling also declines with aging in normal subjects, in this study the influence of regional ventricular diastolic asynchrony on global ventricular filling as a function of age was investigated in 66 normal volunteers aged 19 to 77 years (mean 42) by radionuclide angiography. No subject had systemic hypertension or left ventricular hypertrophy. Indexes of left ventricular systolic function at rest did not vary with age, but rapid diastolic filling significantly declined with age: peak filling rate decreased (r = 0.69), time to peak filling rate increased (r = 0.53) and magnitude of rapid filling (% of left ventricular end-diastolic volume) decreased (r = 0.76) with aging. Left ventricular synchrony was assessed from regional volume curves derived by dividing the global ventricular region of interest into four quadrants. Indexes of systolic synchrony were unaffected by age, but regional variation in time to peak filling rate, an index of diastolic asynchrony, increased with aging (r = 0.51, p less than 0.001). Moreover, variation in time to peak filling rate correlated with global peak filling rate and magnitude of rapid filling (r = 0.48 and 0.54, p less than 0.001 for both). Multivariate analysis indicated that these effects were independent of age-related changes in blood pressure. Thus, aging alters left ventricular diastolic function, with reduced rate and extent of the rapid filling phase related to increased regional diastolic asynchrony.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Long-term serial changes in left ventricular function and reversal of ventricular dilatation after valve replacement for chronic aortic regurgitation.

In most patients with aortic regurgitation, valve replacement results in reduction in left ventricular dilatation and an increase in ejection fraction. To determine the relation between serial changes in ventricular dilatation and changes in ejection fraction, we studied 61 patients with chronic severe aortic regurgitation by echocardiography and radionuclide angiography before, 6-8 months after, and 3-7 years after aortic valve replacement. Between preoperative and early postoperative studies, left ventricular end-diastolic dimension decreased (from 75 +/- 6 to 56 +/- 9 mm, p less than 0.001), peak systolic wall stress decreased (from 247 +/- 50 to 163 +/- 42 dynes x 10(3)/cm2), and ejection fraction increased (from 43 +/- 9% to 51 +/- 16%, p less than 0.001). Between early and late postoperative studies, diastolic dimension and peak systolic wall stress did not change, but ejection fraction increased further (to 56 +/- 19%, p less than 0.001). The increase in ejection fraction correlated with magnitude of reduction in diastolic dimension between preoperative and early postoperative studies (r = 0.63), between early and late postoperative studies (r = 0.54), and between preoperative and late postoperative studies (r = 0.69). Late increases in ejection fraction usually represented the continuation of an initial increase occurring early after operation. Thus, short-term and long-term improvement in left ventricular systolic function after operation is related significantly to the early reduction in left ventricular dilatation arising from correction of left ventricular volume overload. Moreover, late improvement in ejection fraction occurs commonly in patients with an early increase in ejection fraction after valve replacement but is unlikely to occur in patients with no change in ejection fraction during the first 6 months after operation.

Adult↗
PubMed1988

The effect of energy window on cardiac ejection fraction.

ECG gated gamma-ray energy spectra from the left ventricle were created each 50 msec during the cardiac cycle. Nine of ten subjects were studied with a nonimaging Nal probe, and the tenth with a high-resolution Germanium detector. Placing multiple energy windows over the energy spectra, EF was found to vary with the energy window selected. Moving a 20% window across the photopeak produced a roughly linear increase in EF with energy (2.3 EF units per 10 keV increase in energy) in eight of the ten subjects. Dividing the photopeak into a low (126-140 keV) and high-energy (140-154 keV) portion gave significantly different EFs (high energy exceeding low energy by 17%). Increasing the width of a narrow window centered about the photopeak produced negligible change in EF. Examining the energy spectra showed that the small-angle scattered radiation (126-139 keV) was proportionately greater at end systole than at end diastole, after normalizing the spectra to the same photopeak area.

Electrocardiography↗