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Biomedical subjects

R R Miller

Publications and source records attributed to R R Miller.

At least 343 records · Page 19Linked to original sources
PubMed1975

Comparative effects of tolamolol and propranolol on cardiac and peripheral circulatory function in patients with coronary artery disease.

In a clinical study comparing the cardiocirculatroy effects of intravenous tolamolol to those of propranolol, tolamolol, 16 mg, induced similar reduction in resting heart rate as 8 mg propranolol in 16 coronary patients. Tolamolol did not disturb cardiac pump performance and exerted less negative inotropic action than propranolol as assessed by mechanical contractility indices. Myocardial beta-one chronotropic and inotropic stimulation by exogenous epinephrine was blocked equally by tolamolol and propranolol. Tolamolol exerted less systemic vascular beta-two blockade than propranolol as assessed by the peripheral resistance and vasopressor responses to epinephrine infusion. Tolamolction than propranolol and is thereby suitable for careful extension of beta blockade therapy to certain patients with pulmonary and ventricular dysfunction.

Adult↗
PubMed1975

Efficacy of beta adrenergic blockade in coronary heart disease: propranolol in angina pectoris.

Despite widespread clinical application of propranolol (P) in angina pectoris, convincing evidence of its efficacy has been incomplete, thereby resulting in continued controversy. Its antianginal effectivess was investigated in 20 patients with documented coronary heart disease in a 44-wk study incorporating a prolonged 12-wk lead-in period, individualization of P dosage in a 6-wk dose-finding period, and a 24-wk doule-blind crossover phase. On double-blind placebo, patients had 10.5 +/- 2.1 anginal attacks and consumed 12.8 +/- 3.0 nitroglycerin tablets (NTG) each week compared to 6.6 +/- 1.5 anginal episodes (- 37%, p less than 0.001) and 8.0 +/- 1.7 NTG (-38%, p less than 0.001) when on P. No patient experienced more angina with P than with placebo. In addition, time to onset of chest pain during treadmill exercise was prolonged by P from 190 +/- 16 to 248 +/- 22 sec (+31%, p less than 0.02) and ST depression was reduced from 1.7 +/- 0.21 to 0.99 +/- 0.18 mm (-42%, p less than 0.05). There was correlation (r = 0.64 p less than 0.01) between per cent declines in anginal frequency and resting double product with P. Thus, propranolol favorably altered several indices of myocardial ischemia in severe coronary heart disease. This investigation clearly documents the clinical efficacy of optimal beta adrenergic blockade in coronary disease and provides objective justification for the judicious application of propranolol in treatment of angina pectoris.

Adult↗
PubMed1975

Improvement of reduced left ventricular diastolic compliance in ischemic heart disease after successful coronary artery bypass surgery.

To determine the effects of myocardial revascularization on decreased left ventricular diastolic compliance consequent to chronic stable coronary artery disease, 15 patients with patent coronary artery bypass grafts (Group I) were compared with 8 patients with occluded grafts (Group II) studied before and after operation. In addition, eight normal patients served as controls. Left ventricular diastolic compliance was assessed by: (1) total observed diastolic compliance: stroke volume (V) related to left ventricular diastolic pressure (P) change (deltaV/deltaP) normalized for end-systolic volume; (2) left ventricular stiffness index of passive elastic modulus (a equals slope of deltaP/deltaV related to mean left ventricular diastolic pressure); and (3) fractional pattern of left ventricular filling. All patients had normal sinus rhythm and none had preoperative or postoperative mitral regurgitation. The two groups with coronary disease were well matched preoperatively for ventricular function, volumes, mass, segmental contraction and compliance. Ejection fraction increased in Group I (0.56 preoperatively to 0.65 postoperatively, P less than 0.05) but was unchanged in Group II (0.63 To 0.61, P greater 0.05). Postoperative indexes of left ventricular compliance improved in Group I: (1) 0.110 to 0.150 (P less 0.05); (2) 0.030 TO 0.019 (P less 0.05); and (3) 37 to 30 percent filling during last one third of diastole (P less 0.05). These indexes were unchanged postoperatively in Group II: (1) 0.109 to 0.102 (P greater 0.05); (2) 0.033 to 0.039 (P greater than 0.05); and (3) 36 to 41 percent (P greater 0.05). Compliance indexes were not altered (P greater 0.05) in a subset of seven patients in Group I with preoperative or intercurrent myocardial infarction. Thus, this investigation demonstrates the relatively reversible nature of abnormal left ventricular compliance after successful coronary artery bypass surgery in certain patients with ischemic heart disease.

Angiocardiography↗
PubMed1975

Unusual echographic manifestations of right and left heart myxomas.

Although echocardiography has provided a useful noninvasive means for detecting cardiac myxomas, the ultrasound manifestations of these tumors may be variable. We describe our experiences with unusual echographic features encountered in left and right heart myxomas. Thus the left atrial tumor may be manifested predominantly by multiple, discrete, linear echoes behind the mitral valve, the anterior leaflet of which may exhibit an abrupt mid-systolic posterior movement. In right heat myxomatous tumor arising from the septal tricupsid leaflet and adjacent interventricular septum, the echographic characteristics include a cloud of echoes throughout the cardiac cycle in the right ventricular outflow tract which are present in the right ventricle body only during relaxation and are anterior to the tricuspid valve in early diastole. Therefore, discrete linear echoes may be the principal echographic presentation of left atrial myxoma, and special attention should be focused on all areas of the tricuspid valve and right ventricle by ultrasound in patients in whom diagnosis of myxoma is suspected.

Adolescent↗
PubMed1975

Echographic assessment of atrial transport, mitral movement, and ventricular performance following electroversion of supraventricular arrhythmias.

Controversy attends the extent and temporal sequence of improvements in hemodynamic function resulting from the return of atrial contraction following cardioversion of supraventricular arrhythmias. Thus, mitral, left atrial (LA) and left ventricular (LV) echograms were obtained before and one hour after conversion of supraventricular arrhythmias to normal sinus rhythm by direct current countershock in patients with chronic coronary disease or cardiomyopathies without valvular dysfunction. The duration of the rhythm disturbance varied from one day to five years in 22 patients and was indeterminate in 13. Atrial systole immediately produced prominent mitral "A" waves with anterior valve excursion of 7.5 mm (range 3 to 12) in 33 of the 35 patients (94%). The two patients with atrial electromechanical dissociation reverted to atrial fibrillation within one week. Cardioversion caused a decline in LA diameter (3.5 to 3.2 cm, P less than .001) and a rise in LV end-diastolic dimension (5.2 to 5.5 cm, P less than .001) while LV end-systolic dimension was unchanged (4.2 cm). Thereby stroke volume rose. Heart rate fell an average of 16 beats/min. Depressed cardiac output was improved + 0.84 L/min/m-2. Thus, in the majority of patients with acute or chronic supraventricular arrhythmias without mitral valve disease, cardioversion promptly restores effective atrial contraction, decreases LA size, and results in substantial hemodynamic benefit.

Adult↗
PubMed1975

Clinical use of sodium nitroprusside in chronic ischemic heart disease. Effects on peripheral vascular resistance and venous tone and on ventricular volume, pump and mechanical performance.

Although hemodynamic benefit has been shown with sodium nitroprusside (NP) in acute coronary pump failure, complete understanding of the mechanisms of action of the agent on the cardiocirculation and its value in chronic ventricular dysfunction are lacking. This investigation evaluates the effects of NP on the systemic and regional arterial and venous beds and on cardiac dynamics, ventricular volumes, contractile state and myocardial energetics in long-standing congestive heart failure. Twelve patients with chronic coronary pump dysfunction received NP infusion to lower systolic pressure to 95-105 mm Hg. Left ventricular (LV) function was assessed directly by angiographic volumes and high fidelity pressure, and peripheral circulatory dynamics were determined simultaneously by forearm arterial and venous plethysmography. NP reduced mean arterial pressure (MAP) from 88.2 to 73.4 mm Hg (P less than 0.05) and significantly (P less than 0.05) enhanced the variables of LV performance: LV end-diastolic pressure (EDP) diminished from 18.5 to 9.9 mm Hg; ejection fraction rose from 0.47 to 0.55; percent of LV segmental shortening increased; and isovolumic and ejection indices of contractility improved. Concomitantly, NP reduced the indices of myocardial oxygen demands of ventricular tension time index and LVED volume index. These salutary effects on LV performance and energetics occurred secondary to peripheral arterial and venous dilation (P less than 0.05) produced by NP: total systemic vascular resistance was lowered from 1590 to 1310 dynes sec cm--5; forearm vascular resistance diminished from 46 to 37 mm Hg/ml/100 gm/min; and forearm venous tone fell from 14.2 to 10.1 mm Hg/cc. Depressed stroke index (SI) and cardiac index (CI) increased (P less than 0.05) with NP: despite the fall in LVEDP, when ventricular filling pressures with the agent were at levels slightly above normal. Dextran infusion given with NP to restore LVEDP to moderately elevated values increased SI and CI (P less than 0.05) when NP alone produced no change in stroke output. Thus, the peripheral vasodilator properties of nitroprusside improve LV function by reducing impedance to ventricular ejection, while MVO2 is diminished by decreasing LV preload and afterload through relaxing actions

Adult↗
PubMed1975

Echography and phonography of acute aortic regurgitation in bacterial endocarditis.

Since management of acute aortic regurgitation in bacterial endocarditis is enhanced by early recognition, echocardiography and phonocardiography were evaluated in three such cases documented by catheterization and surgery without positive blood cultures and compared to echophonograms of 34 patients with aortic regurgitation of other origins. Endocarditis manifested distinctive, thickened, irregular aortic leaflet echoes with normal systolic excursion and mitral echopreclosure with anterior leaflet fluttering. Mitral preclosure resulted in mid- or end-diastolic crescendo murmur accompanied by soft first heart sound. Aortic echograms in nonendocarditis showed either widened root, diminished leaflet excursion, absence of irregular valvular thickening, or normal leaflets, all without mitral preclosure. This study shows specific echophonographic findings of aortic regurgitation due to endocarditis that enable diagnosis of this condition in the absence of positive blood cultures.

Acute Disease↗
PubMed1975

Pharmacotherapy of essential hypertension.

Practical clinical aspects of the evaluation and treatment of essential hypertension are reviewed. Drug therapy discussed includes diuretics, and as adjunctive therapy, sympathoplegic agents, peripheral vasodilators and beta blockers. Also covered are treatment of less common forms of essential hypertension, other forms of antihypertensive therapy, and the use of fixed combinations of antihypertensive drugs.

Adrenergic beta-Antagonists↗