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Biomedical subjects

R O Bonow

Publications and source records attributed to R O Bonow.

At least 163 records · Page 9Linked to original sources
PubMed1987

Prognostic implications of symptomatic versus asymptomatic (silent) myocardial ischemia induced by exercise in mildly symptomatic and in asymptomatic patients with angiographically documented coronary artery disease.

Patients with coronary artery disease (CAD) may undergo periods of reversible myocardial ischemia without experiencing angina. To study the prognostic implications of "silent" myocardial ischemia induced by exercise, exercise electrocardiography and radionuclide angiography were performed in 131 consecutive patients with CAD, preserved left ventricular (LV) function at rest and mild or no symptoms during medical therapy. All patients who died during medical therapy were in the subgroup of patients with 3-vessel CAD in whom exercise-induced ischemia developed, which was characterized by both a decrease in LV ejection fraction and ST-segment depression. Patients in whom angina pectoris developed during exercise (54% of all patients) had a greater prevalence of this combined ischemic response to exercise than patients without angina (61% vs 27%, p less than 0.001) and also a greater prevalence of left main or 3-vessel CAD (59% vs 25%, p less than 0.001). However, when inducible ischemia was demonstrated, risk stratification and prognosis were the same whether the ischemic episode was symptomatic or silent. Among patients having both a reduction in ejection fraction and a positive ST-segment response, the likelihood of significant left main narrowing (13% vs 26%), 3-vessel CAD (56% vs 51%) and death during subsequent medical therapy (16% vs 9%) was similar in patients with silent compared to those with symptomatic ischemia. These data indicate that patients in whom angina develops during exercise have a greater prevalence of high-risk coronary anatomy and of inducible ischemia than patients without angina. However, once inducible ischemia is documented, the symptomatic response to exercise appears irrelevant for prognostic or risk stratification considerations.

Aged↗
PubMed1987

Occurrence and significance of progressive left ventricular wall thinning and relative cavity dilatation in hypertrophic cardiomyopathy.

This investigation was undertaken to assess the prevalence of systolic dysfunction, left ventricular (LV) wall thinning and cavity enlargement in a large population of patients with hypertrophic cardiomyopathy (HC), and to determine the role of these conditions in the natural history of this disease. Of 217 consecutively studied patients with HC, most of whom were severely symptomatic, 197 (91%) had an LV ejection fraction of 50% or more and 20 (9%) had an ejection fraction of less than 50% as assessed with radionuclide angiography. Changes in LV wall thickness and cavity dimension were evaluated using serial M-mode and 2-dimensional echocardiography over an average follow-up of 3.6 years in 67 of the 217 patients (54 with ejection fraction of greater than or equal to 50% and 13 with ejection fraction less than 50%). A substantial decrease (at least 5 mm) in LV wall thickness was seen in 8 of the 13 patients (62%) with an ejection fraction greater than or equal to 50%, but in only 2 of the 54 patients (4%) with an ejection fraction greater than or equal to 50% (p less than 0.001). LV cavity dimension increased significantly over the period of follow-up in the 13 patients with depressed ejection fraction (from 44 +/- 5 to 49 +/- 7 mm, p less than 0.005); however, absolute cavity size remained normal (less than or equal to 52 mm or less) in 10 of these 13 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Significance of abnormal blood pressure response during exercise-induced myocardial dysfunction after recent acute myocardial infarction.

The relation between exercise left ventricular ejection fraction and blood pressure (BP) responses after an acute myocardial infarction (AMI) was investigated. Twenty-eight to 37 days after an uncomplicated AMI, 224 consecutive patients underwent exercise radionuclide angiography in the 40 degrees semisupine position. In 180 patients (group A, 80%), BP increased more than 5 mm Hg every stage; in 44 patients, BP responses were abnormal; in 33 (group B, 15%), BP did not increase during 2 stages; in 11 (group C, 5%), it decreased more than 5 mm Hg after an initial increase. Ejection fraction did not differ significantly among the 3 groups at rest (51 +/- 13 in group A, 50 +/- 18 in group B, 47 +/- 13 in group C [difference not significant]) or at peak exercise (51 +/- 16% in group A, 46 +/- 19% in group B, and 43 +/- 16% in group C, [difference not significant]). Exercise-induced left ventricular failure or hemodynamic decompensation occurred in 22 patients. In these patients, ejection fraction at rest was 44 +/- 19% and decreased to 35 +/- 16% (p less than 0.05) with exercise. Only 9 of these patients (41%) had abnormal BP responses, with the other 13 (59%) showing a normal BP responses. The The 35 patients with abnormal BP responses in the absence of hemodynamic decompensation were asymptomatic, terminating exercise because of fatigue. The ejection fraction at rest and during exercise in these patients was similar to that in patients with normal BP responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Determinants of ventricular arrhythmias in mildly symptomatic patients with coronary artery disease and influence of inducible left ventricular dysfunction on arrhythmia frequency.

To determine the relation among ventricular arrhythmias, prognostic factors and reversible ischemia in coronary artery disease, 131 drug-free, minimally symptomatic patients were studied by radionuclide angiography and 24 hour Holter electrocardiographic monitoring. High grade ventricular arrhythmias (couplets, salvos of premature ventricular complexes and R on T phenomenon) were observed in 33 patients (25%) and were related to lower rest and exercise ejection fraction, greater number of stenotic coronary arteries and higher prevalence of regional wall motion abnormalities at rest (all p less than or equal to 0.1). Among patients with subnormal rest ejection fraction, high grade arrhythmias occurred with greater prevalence in those with reversible left ventricular dysfunction (reduction in ejection fraction) during exercise compared with those with a normal ejection fraction response (59 versus 23%, p less than 0.05), a relation observed principally in patients with multivessel disease. These data indicate that in minimally symptomatic patients with coronary artery disease, arrhythmias are related to both extent of disease and severity of regional and global ventricular dysfunction and are most prevalent in patients with ventricular dysfunction and evidence of inducible ischemia, factors indicating poor long-term prognosis during medical therapy.

Adult↗
PubMed1987

Three year anatomic, functional and clinical follow-up after successful percutaneous transluminal coronary angioplasty.

Because the long-term anatomic effects of percutaneous transluminal coronary angioplasty are unknown, follow-up evaluations including coronary angiography, treadmill exercise testing and rest and bicycle exercise radionuclide angiography were performed in 46 patients 6.3 +/- 2.0 and 37.6 +/- 3.6 (mean +/- SD) months after they had undergone successful single lesion angioplasty. The severity of the coronary stenosis decreased significantly at each evaluation; the mean diameter stenosis was 66 +/- 13% before angioplasty, 30 +/- 13% immediately after and 26 +/- 16% and 19 +/- 13% at 6 months and 3 years, respectively. Exercise time increased from 9.8 +/- 4.4 minutes before angioplasty to 18.3 +/- 4.5 minutes immediately after the procedure and remained at that level at 6 months (20.3 +/- 4.6 minutes) and 3 years (18.2 +/- 4.5 minutes). Left ventricular ejection fraction during exercise decreased 4 +/- 6% compared with rest before angioplasty, but increased 7 +/- 7% immediately after angioplasty and this increase was maintained at 6 months (+/- 6 +/- 7%) and 3 years (+/- 4 +/- 6%). Before angioplasty, 1 patient was in Canadian Heart Association functional class 0, 15 were in class II, 24 in class III and 6 in class IV. Three years later, 25 were in class 0, 10 in class I, 7 in class II and 4 in class III. These results indicate that the short-term anatomic and functional success of coronary angioplasty is maintained for at least 3 years.

Adult↗
PubMed1987

Noninvasive assessment of left ventricular diastolic function by pulsed Doppler echocardiography in patients with hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy is a primary myocardial disease in which symptoms may frequently result from impaired left ventricular relaxation, filling and compliance. In the present investigation, Doppler echocardiography was utilized to measure transmitral flow velocity and thereby assess left ventricular diastolic performance noninvasively in a group of 111 patients representative of the broad clinical spectrum of hypertrophic cardiomyopathy. In patients with hypertrophic cardiomyopathy, all Doppler indexes of diastolic relaxation and filling differed significantly (p less than 0.001) from those obtained in 86 control subjects without heart disease, namely, prolongation of isovolumic relaxation (94 +/- 24 versus 78 +/- 12 ms) and of the early diastolic peak of flow velocity (244 +/- 55 versus 220 +/- 28 ms), as well as slower deceleration (3.4 +/- 1.4 versus 4.9 +/- 1.3 m/s2) and reduced maximal flow velocity in early diastole (0.5 +/- 0.2 versus 0.6 +/- 0.1 m/s). As an apparent compensation for impaired relaxation and early diastolic filling, the atrial contribution to left ventricular filling was increased, as shown by increased late diastolic flow velocity (0.4 +/- 0.3 versus 0.3 +/- 0.1 m/s) and reduced ratio of maximal flow velocity in early diastole to that in late diastole (1.4 +/- 0.8 versus 2.1 +/- 0.9). The vast majority of patients with hypertrophic cardiomyopathy (91 [82%] of 111) showed evidence of impaired left ventricular diastolic performance, as assessed from the Doppler waveform. Abnormal Doppler diastolic indexes were identified with similar frequency in patients with (78%) or without (83%) left ventricular outflow obstruction, as well as in patients with (84%) or without (80%) cardiac symptoms. However, patients with nonobstructive hypertrophic cardiomyopathy showed more severe alterations in the Doppler indexes of diastolic function than did patients with obstruction. Thus, abnormal diastolic performance as assessed by Doppler echocardiography was apparent in the vast majority of the study patients with hypertrophic cardiomyopathy, independent of the presence or absence of cardiac symptoms or a subaortic pressure gradient. The high frequency with which diastolic abnormalities are identified in asymptomatic patients with hypertrophic cardiomyopathy suggests that impaired diastolic performance may be present at a time in the natural history of the disease when functional limitation is not yet evident.

Adolescent↗
PubMed1987

Regional left ventricular asynchrony and impaired global left ventricular filling in hypertrophic cardiomyopathy: effect of verapamil.

Left ventricular relaxation and filling are impaired in many patients with hypertrophic cardiomyopathy. To investigate the influence of regional heterogeneity on these global abnormalities, 48 patients with hypertrophic cardiomyopathy and sinus rhythm were studied by radionuclide angiography before and after 1 to 2 weeks of verapamil therapy (320 to 640 mg/day, median 480). Left ventricular regional function was assessed by subdividing the ventricular region of interest into 20 sectors and into four quadrants from which regional time-activity curves were derived. Diastolic asynchrony was measured as the regional variation in timing between minimal volume and peak filling rate, and heterogeneity in the magnitude of rapid diastolic filling was measured as the regional variation in percent contribution of atrial systole to end-diastolic volume. Compared with 28 normal subjects, the patients with hypertrophic cardiomyopathy had greater regional variation in both timing (35 +/- 24 versus 12 +/- 6 ms, p less than 0.001) and magnitude (10 +/- 6 versus 7 +/- 4%, p less than 0.02) of rapid filling. Verapamil reduced the regional variation in timing (to 21 +/- 16 ms, p less than 0.001) and magnitude (to 7 +/- 3%, p less than 0.001) of rapid filling. These regional changes, indicating more uniform regional diastolic performance after verapamil, were associated with improved global diastolic filling: global rapid filling increased in both rate and magnitude and time to peak filling rate decreased. These findings indicate that the beneficial effect of verapamil on left ventricular diastolic function in hypertrophic cardiomyopathy may be mediated by reduction in regional asynchrony.

Adult↗
PubMed1987

Myocardial perfusion abnormalities in patients with hypertrophic cardiomyopathy: assessment with thallium-201 emission computed tomography.

Myocardial ischemia may play a critical role in the symptomatic presentation and natural history of hypertrophic cardiomyopathy (HCM). To assess the relative prevalence and functional significance of myocardial perfusion abnormalities in patients comprising the broad clinical spectrum of HCM, we studied 72 patients (ages 12 to 69 years, mean 40) using thallium-201 emission computed tomography. Imaging was performed immediately after maximal exercise and again after a 3 hr delay. Regional perfusion defects were identified in 41 of the 72 patients (57%). Fixed or only partially reversible defects were evident in 17 patients, 14 of whom (82%) had left ventricular ejection fractions of less than 50% at rest. Twenty-four patients demonstrated perfusion defects during exercise that completely reversed at rest; all had normal or hyperdynamic left ventricular systolic function (ejection fraction greater than or equal to 50%). Perfusion abnormalities were present in all regions of the left ventricle. However, the fixed defects were observed predominantly in segments of the left ventricular wall that were of normal or only mildly increased (15 to 20 mm) thickness; in contrast, a substantial proportion (41%) of the completely reversible defects occurred in areas of moderate-to-marked wall thickness (greater than or equal to 20 mm, p less than .001). Neither a history of chest pain nor its provocation with treadmill exercise was predictive of an abnormal thallium study, since regional perfusion defects were present in 10 of 18 (56%) completely asymptomatic patients, compared with 31 of 54 (58%) symptomatic patients. These data indicate that myocardial perfusion abnormalities occur commonly among patients with HCM. Fixed or only partially reversible defects suggestive of myocardial scar and/or severe ischemia occur primarily in patients with impaired systolic performance. Completely reversible perfusion abnormalities occur predominantly in patients with normal or supranormal left ventricular systolic function. Such dynamic changes in regional thallium activity may reflect an ischemic process that contributes importantly to the clinical manifestations and natural history of HCM.

Adolescent↗
PubMed1986

Prospective evaluation of doxorubicin cardiotoxicity by rest and exercise radionuclide angiography.

The role of rest and exercise radionuclide angiography (RNA) in predicting the cardiotoxic effects of doxorubicin was assessed prospectively in 48 patients who received a mean total doxorubicin dose of 522 mg/m2 (range 480 to 600). Thirty-three of these patients also received cyclophosphamide (mean 5,220 mg/m2). Left ventricular (LV) ejection fraction (EF) at rest progressively decreased from the baseline value of 55 +/- 9% to 52 +/- 8% after 338 mg/m2 to 47 +/- 8% after completion of doxorubicin therapy (p less than 0.001). In 42 patients (88%) EF at rest decreased after doxorubicin administration. Although no patient had known prior heart disease, the EF response to exercise was abnormal in 11 patients before doxorubicin. EF at rest after doxorubicin was significantly lower (41 +/- 6% vs 49 +/- 8%, p less than 0.02) in these 11 patients than in the 29 patients in whom the pretreatment EF response to exercise was normal, and in 4 of the 11 patients congestive heart failure developed. While age was an independent risk factor, cyclophosphamide did not appear to enhance the cardiotoxicity of doxorubicin. By multivariate analysis, age (p = 0.01) and EF at the midcourse of doxorubicin therapy (p less than 0.001) were the most significant predictors of final EF after completion of doxorubicin therapy; neither rest nor exercise EF before doxorubicin appreciably improved the predictive value of age and EF at midcourse of therapy. Thus, some depression of LV function occurs in most patients receiving doxorubicin, and patients with abnormal baseline function appear to be at greater risk of clinical congestive heart failure after doxorubicin therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Prospective study of cardiomyopathy induced by adjuvant doxorubicin therapy in patients with soft-tissue sarcomas.

Since a combination of surgery and adjuvant high-dose doxorubicin therapy can prolong survival in patients with extremity sarcomas, but at the expense of significant cardiomyopathic changes, we prospectively studied the differences in cardiotoxicity in 118 patients with sarcomas treated with high- vs low-dose doxorubicin therapy following surgery. Cardiac function, as assessed by left ventricular ejection fraction (EF), was determined by standard radionuclide angiography during rest and exercise. No patients in this study developed congestive heart failure. While both regimens produced net decreases in EF during rest and exercise, the high-dose doxorubicin regimen resulted in significantly greater declines in EF than the low-dose protocol. Of patients with normal baseline values, a greater percentage of patients receiving the high-dose regimen developed an abnormal EF than did those receiving the low-dose regimen, even after separating younger from older individuals. Thus, treatment-induced cardiomyopathy appears to be a significant clinical problem after both high- and low-dose doxorubicin therapy. The use of the low-dose regimen decreases the magnitude of the cardiomyopathic changes.

Adult↗
PubMed1986

Severe functional limitation in patients with hypertrophic cardiomyopathy and only mild localized left ventricular hypertrophy.

Ten patients with nonobstructive hypertrophic cardiomyopathy and only mild localized left ventricular hypertrophy who had severe symptoms of cardiac failure are described. During a mean follow-up period of 7 years, 6 of these 10 patients showed a substantial increase in left ventricular internal dimension (6 to 15 mm, mean 10) as assessed with M-mode echocardiography, although absolute left ventricular cavity size remained within normal limits in 5 of the 6. Four patients demonstrated substantial septal thinning (5 to 14 mm, mean 8). Left ventricular diastolic function, assessed by radionuclide angiography in nine patients, was impaired in eight who showed decreased peak filling rate (less than 2.5 end-diastolic volumes/s) and prolonged time to peak rate of filling (greater than or equal to 180 ms). Furthermore, left ventricular systolic function, usually supernormal in patients with hypertrophic cardiomyopathy, was depressed (ejection fraction less than or equal to 45%) in six patients. Hence, a subset of patients was identified with nonobstructive hypertrophic cardiomyopathy and only mild localized left ventricular hypertrophy who experienced severe cardiac symptoms. The majority of these patients showed both systolic and diastolic left ventricular dysfunction in the presence of a progressive increase in left ventricular internal dimension (but without absolute left ventricular dilation) or ventricular septal thinning or both. Such patients may represent an important component of the natural history of hypertrophic cardiomyopathy which has not been previously fully appreciated.

Adolescent↗
PubMed1986

Isovolumic relaxation period in hypertrophic cardiomyopathy: assessment by radionuclide angiography.

Left ventricular isovolumic relaxation and the relation between relaxation and filling were studied in 90 patients with hypertrophic cardiomyopathy and 29 control subjects using radionuclide angiography. The isovolumic relaxation period was determined automatically on left ventricular time-activity curves as the interval between minimal volume and onset of rapid filling. In 17 patients, M-mode echocardiography performed simultaneously with radionuclide angiography demonstrated that onset of mitral valve opening correlated well with onset of rapid filling (r = 0.84, p less than 0.001). The isovolumic relaxation period was longer in patients with hypertrophic cardiomyopathy than in control subjects (95 +/- 44 versus 50 +/- 23 ms, p less than 0.01) and was longer in patients without an outflow tract gradient at rest than in patients with a gradient (109 +/- 37 versus 86 +/- 35 ms, p less than 0.05). In these patients without obstruction, a weak linear relation between duration of the isovolumic period and peak filling rate was found (r = 0.48, p less than 0.02). Filling was impaired in patients with hypertrophic cardiomyopathy, as assessed by lower peak filling rate (3.2 +/- 1.2 versus 3.5 +/- 0.5 end-diastolic volume/s, p less than 0.05) and prolonged time to peak filling rate (185 +/- 44 versus 145 +/- 20 ms, p less than 0.01) compared with values in control subjects. The delay in time to peak filling rate was caused primarily by the prolonged isovolumic period, because the interval from onset of rapid filling to peak filling rate was similar in patients with hypertrophic cardiomyopathy and control subjects (87 +/- 31 versus 95 +/- 25 ms, NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Noninvasive assessment of left ventricular diastolic function: comparative analysis of Doppler echocardiographic and radionuclide angiographic techniques.

This investigation was performed to determine whether variables obtained directly from the Doppler left ventricular diastolic flow velocity profile provide a reliable estimate of diastolic function. Measurements of diastolic flow velocity obtained by Doppler echocardiography were compared with volumetric measurements of left ventricular diastolic filling determined by radionuclide angiography in 12 subjects without cardiac disease and in 25 patients with a variety of cardiac diseases. The two methods were in agreement in distinguishing normal from abnormal diastolic function in 21 (84%) of the 25 patients with cardiac disease, identifying diastolic function as normal in 8 and abnormal in 13 of these patients. Good correlations were observed between certain Doppler variables of left ventricular diastolic flow velocity and radionuclide angiographic variables of left ventricular filling. The time interval from the aortic closing component of the second heart sound to the end of the early diastolic flow velocity peak, assessed with Doppler echocardiography, correlated well with the time interval from end-systole to the end of rapid filling, assessed with radionuclide angiography (r = 0.83). Descent of the Doppler early diastolic flow velocity peak correlated well with the radionuclide angiographic peak filling rate (r = 0.79). The ratio between the heights of the early and late (due to atrial systole) peaks of diastolic flow velocity showed good correlation with the ratio between percent of left ventricular filling during rapid filling and during atrial systole (r = 0.76). These findings demonstrate that the left ventricular diastolic flow velocity profile obtained with Doppler echocardiography compares favorably with radionuclide angiographic variables in the evaluation of left ventricular diastolic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Left ventricular pulsus alternans in patients with hypertrophic cardiomyopathy and severe obstruction to left ventricular outflow.

Left ventricular pulsus alternans (LVPA), a rhythmic beat to beat variation in left ventricular systolic pressure and outflow gradient, was noted in 35 of 200 ventricular systolic pressure and outflow gradient, was noted in 35 of 200 patients with hypertrophic cardiomyopathy undergoing hemodynamic study. LVPA was not associated with significant systemic pulsus alternans nor right ventricular pulsus alternans. All patients with LVPA had severe outflow gradients at rest or during provocation. Of 61 patients with severe basal outflow gradients (greater than 80 mm Hg), 12 demonstrated LVPA at rest. Eight of these patients underwent ventricular septal myotomy-myectomy; all had successful abolition of basal outflow gradient. Of the seven of these eight patients who underwent postoperative hemodynamic study and who were in sinus rhythm, none demonstrated LVPA. Eleven of 60 patients with basal outflow gradients ranging from 10 to 70 mm Hg demonstrated LVPA during maneuvers provocative for outflow gradients (mean gradient 90 +/- 37 mm Hg). Two of these patients underwent ventricular septal myotomy-myectomy; neither had a gradient nor LVPA during provocation postoperatively. Twelve additional patients with basal outflow gradients ranging from 0 to 115 mm Hg had LVPA after ectopic beats, generally occurring during maneuvers provocative for outflow gradients, associated with severe outflow gradients (mean gradient 130 +/- 39 mm Hg) during the postextrasystolic beat. None of the 41 patients without an outflow gradient, basal or during provocation, was found to have LVPA. Thus LVPA is commonly seen in during provocation, was found to have LVPA. Thus LVPA is commonly seen in patients with hypertrophic cardiomyopathy and severe left ventricular outflow gradients and may represent inadequate left ventricular contractile function in the presence of high left ventricular systolic pressures.

Adult↗