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Biomedical subjects

R M Becker

Publications and source records attributed to R M Becker.

15 recordsLinked to original sources
PubMed1979

Mechanism of reduction of mitral regurgitation with vasodilator therapy.

Acute mitral regurgitation was produced in six open chest dogs by excising a portion of the anterior valve leaflet. Electromagnetic flow probes were placed in the left atrium around the mitral anulus and in the ascending aorta to determine phasic left ventricular filling volume, regurgitant volume and stroke volume. The systolic pressure gradient was calculated from simultaneously measured high fidelity left atrial and left ventricular pressures. The effective mitral regurgitant orifice area was calculated from Gorlin's hydraulic equation. Infusion of nitroprusside resulted in a significant reduction in mitral regurgitation. No significant change occurred in the systolic pressure gradient between the left ventricle and the left atrium because both peak left ventricular pressure and left atrial pressure were reduced. The reduction of mitral regurgitation was largely due to reduction in the size of the mitral regurgitant orifice. Reduction of ventricular volume rather than the traditional concept of reduction of impedance of left ventricular ejection may explain the effects of vasodilators in reducing mitral regurgitation.

Animals↗
PubMed1979

Dynamic aspects of acute mitral regurgitation: effects of ventricular volume, pressure and contractility on the effective regurgitant orifice area.

The dynamics of acute mitral regurgitation were studied in six open-chest dogs in whom a portion of the anterior leaflet was excised. Phasic mitral and aortic flows were measured electromagnetically and left ventricular filling volume, regurgitant volume (RV) and forward stroke volume (SV) were calculated. The systolic pressure gradient (SPG) between the left ventricle (LV) and left atrium (LA) was obtained from high-fidelity pressure transducers. The effective mitral regurgitant orifice area (MRA) was calculated from the hydraulic equation of Gorlin. Volume infusion resulted in significant increases in both left atrial and left ventricular pressures; thus, the SPG was unchanged and the increase in RV was due primarily to the increase in MRA. Angiotensin infused to raise arterial pressure resulted in greater increments in left ventricular than left atrial pressure, so that SPG rose significantly. The increase in RV was due to increases in both MRA and SPG. Norepinephrine infusion increased systolic left ventricular pressure and SPG, while left ventricular end-diastolic pressure and left atrial pressure diminished. Despite a significant increase in SPG, RV did not increase, due to a substantial decrease in MRA. Thus, angiotensin and volume infusion induced a substantial increase in regurgitation due to the increase in MRA, while augmentation of contractility after norepinephrine infusion resulted in a decrease in regurgitation through reduction of MRA. These findings support the clinical view that maintaining a small LV with sustained myocardial contractility will reduce mitral regurgitation. Alternatively, left ventricular dilatation can enhance mitral regurgitation by increasing the effective regurgitant orifice independent of SPG.

Angiotensin II↗
PubMed1979

beta-Blockade therapy for supraventricular tachyarrhythmias after coronary surgery: a propranolol withdrawal syndrome?

A high incidence of cardiac arrhythmias and hypertension has been noted after coronary artery bypass surgery in patients previously treated with oral propranolol. Forty-two patients undergoing coronary bypass surgery had propranolol withdrawal 10 hours before surgery and were randomized into a group treated with propranolol immediately postoperatively, and a nontreatment group. Patients treated with prophylactic propranolol had a significantly lower incidence of postoperative supraventricular arrhythmias compared to patints who received no prophylaxis. All the arrhythmias responded rapidly to 1 mg of intravenous propranolol therapy, whether it was used as a primary treatment or as a supplement to prophylactic propranolol. The findings suggest that (1) there is a high incidence of supraventricular arrhythmias and sinus tachycardia after coronary artery bypass which might reflect an abrupt propranolol withdrawal, and (2) that perioperative prophylactic or supplementary propranolol therapy will successfully prevent or treat most of these arrhythmias.

Coronary Artery Bypass↗
PubMed1979

Surgery for mitral valve endocarditis.

The records of 20 patients who underwent mitral valve replacement for complications of bacterial endocarditis were reviewed. Although the indications for surgery were the same as those for patients with aortic endocarditis, major emboli (cerebral, coronary or retinal) prompted surgery in 8 of 20 patients, a much higher incidence than reported for surgery in aortic valve endocarditis. Eighteen of the patients had mitral regurgitation; 14 of these had severe congestive heart failure, but the development of congestive failure tended to be more insidious than in patients with aortic endocarditis. Continued septicemia despite appropriate antibiotics was the least common indication for surgery. Sixteen of the 20 patients were salvaged by surgery, although some had major residual deficits, related mainly to preoperative emboli. These results are a marked improvement in the expected 90-100 percent mortality rate for patients with these complications of endocarditis. The main reason for a poor result following surgery was temporization leading to continued deterioration of vital functions preoperatively. Reinfection of the prosthesis did not occur, and we do not consider duration of preoperative antibiotic therapy an important factor in the decision to perform surgery.

Adult↗
PubMed1978

In vitro hydrodynamic comparison of mitral valve prostheses at high flow rates.

A pulse duplicator system for evaluating the hemodynamic performance of mitral prostheses is described. Under conditions stimulating normal resting physiology, all valves tested had measurable but acceptably small pressure drops. Under conditions simulating exercise, all were moderately to severely stenotic. Valves with nearly equal mounting diameters were compared. The Hancock, Beall, and Starr-Edwards valves (Group A) were found to be significantly more stenotic than the Björk-Shiley, Cutter-Cooley, Ionescu-Shiley, and Lillehei-Kaster valves (Group B). In the 29 to 30 mm. mounting diameter size at cardiac outputs of 5 and 9 L. per minute, Group A had average pressure drops of 3.2 and 10.5 mm. Hg and Group B, pressure drops of 1.6 and 5.3 mm. Hg, respectively. In the 24 to 26 mm. mounting diameter size, at cardiac outputs of 9 L. per minute, all the valves had critically large pressure drops (9 to 17.6 mm. Hg). The standard Gorlin formula is inappropriate for computing the orifice area of prosthetic valves. The discharge coefficient for a valve (a measure of how well the valve uses its primary flow area) and a performance index (a measure of how well the valve uses its mounting area) have been computed from a knowledge of the orifice size, without the necessity of assuming a value for the discharge coefficient required by the Gorlin formula. The biological valves (Hancock and Ionescu-Shiley) provide an efficient orifice for fluid flow at the free leaflet margins and have large discharge coefficients. On the basis of the fluid dynamic equation of motion, steady flow, root mean square (RMS) flow, and peak flow, combined with the appropriate transvalvular gradients, were all shown to yield equally accurate characterizations of valvular hydrodynamic performance. Mean flow, unfortunately the only value obtainable clinically, yielded effective orifice areas 10 percent smaller than either of the other three flow values.

Bioprosthesis↗
PubMed1976

Transaxillary minithoracotomy: the optimal approach for certain pulmonary and mediastinal lesions.

This report concerns the use of transaxillary thoracotomy for a variety of pulmonary, pleural, and mediastinal conditions in 50 patients. Primary and metastatic carcinomas, pneumothoraces, and benign lesions such as bronchogenic cysts and neurogenic tumors can be identified, evaluated, and treated with confidence. Reduced postoperative pain and morbidity, rapid return of arm and shoulder movements, reduced hospital stay, and excellent cosmetic result are among the advantages of this approach when compared with the usual posterolateral thoracotomy.

Axilla↗
PubMed1976

Congenital esophagobronchial fistula in a 62-year-old woman.

A 62-year-old woman had symptoms of cough provoked by ingestion of liquids and radiologic changes compatible with repeated bouts of aspiration pneumonitis. A left bronchoesophageal fistula was easily demonstrated by barium esophagogram and fiberoptic bronchoscopy. Division of the fistula resulted in immediate disappearance of the symptoms, gradual resolution of the radiologic abnormalities, and marked improvement in the results of pulmonary function tests. The fistula appeared to be of congenital origin, but the reason that symptoms developed so late in life remains obscure.

Bronchial Fistula↗
PubMed1976

Multiple pulmonary leiomyomatous hamartomas in women.

A rare case of multiple pulmonary leiomyomatous hamartomas is described and seven previously reported cases are reviewed. The pathological and clinical features of this lesion, which is benign and occurs in middle-aged women, are unique; a conservative approach following the establishment of diagnosis is recommended.

Female↗
PubMed1976

Infected aortic bifurcation grafts: experience with fourteen patients.

The experience with 14 patients with infected aortic bifurcation grafts has been reviewed. Factors which appeared to predispose to infection in 11 patients included "re-do" operations, concomitant cholecystectomy or gastrostomy, and ruptured abdominal aneurysm. A mixture of gastrointestinal organisms was responsible for the infections. The pathogenesis, presentation, and treatment varied according to whether the proximal or distal anastomosis was involved or not. Aortoduodenal communications were present in five patients; they presented with gastrointestinal bleeding or septicemia. One patient survived as a result of early, aggressive surgical therapy. Infection presented at the distal anastomosis in nine patients, either as groin abscess or false aneurysm. Conservative therapy failed in the majority of patients but apparently was successful in three of five patients in whom infection did not involve the intra-abdominal portion of the graft. When infection does involve the intra-abdominal portion of the graft, then the graft must be excised also. Revascularization often can be accomplished with extra-anatomic bypasses of prosthesis or autogenous material, depending on the characteristics of the individual patient. Regardless of the mode of presentation or the site of infection, the early institution of judicious surgical management offers the best chance of success in these patients, and temporization usually leads to failure.

Aortic Aneurysm↗