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Biomedical subjects

F H Levine

Publications and source records attributed to F H Levine.

At least 37 records · Page 2Linked to original sources
PubMed1981

Correlation of patterns of subendocardial reperfusion and left ventricular performance after ischemia.

Ninety-three dogs were studied with normothermic or hypothermic ischemia for 60 or 90 minutes, with or without potassium cardioplegia. Radioactive-labeled microspheres (9 +/- 1) were injected into the aortic perfusion cannula just prior to aortic cross-clamping and at 2, 6, and 10 minutes after the clamp was released. Left ventricular (LV) function was analyzed with a right heart bypass model before and 45 minutes after the ischemia period. Changes in LV function were defined as the arithmetic difference in the center of mass between preischemia and postischemia computer-drawn Sarnoff curves. Regardless of technique of myocardial protection, increased subendocardial flow 2 minutes after ischemia correlated strongly with preservation of LV function (p less than 0.01). Well-preserved hearts showed a rapid return to normal levels of coronary blood flow (p less than 0.01). In contrast, a delay in the peaking of subendocardial flow to 10 minutes was associated with poor function (p less than 0.01). There was a high correlation between ultrastructural morphology and LV function. While well-preserved hearts showed early preferential subendocardial perfusion, the poorly protected myocardium is unable to restore adequate subendocardial flow early in the reperfusion period.

Animals↗
PubMed1981

Plasma vasopressin levels and urinary sodium excretion during cardiopulmonary bypass with and without pulsatile flow.

The use of pulsatile perfusion during bypass should create a more physiological milieu and thus attenuate the vasopressin stress response. To determine this, 20 patients scheduled for elective coronary artery bypass operation were studied in two groups. Group 1 had a standard nonpulsatile perfusion, and in Group 2 a pulsatile pump was used. Measurements were made before and after anesthesia, after surgical incision, and at 15 and 30 minutes during and after cardiopulmonary bypass. In both groups, vasopressin levels were significantly elevated after sternotomy (4.5 +/- 1.5 to 37 +/- 10 pg/ml in Group 1 and 3.1 +/- 1.2 to 33 +/- 9 pg/ml in Group 2, p less than 0.05) and during bypass (198 +/- 19 pg/ml in Group 1 and 113 +/- 16 pg/ml in Group 2) but were higher in Group 1 (p less than 0.05). With comparable perfusion pressures in both groups, Group 2 required higher flow (4.2 +/- 0.2 versus 3.5 +/- 0.3 L/min, p less than 0.05) and had lower resistance (1,351 +/- 182 versus 1,841 +/- 229 dynes sec cm-5, p less than 0.05) and higher urine Na+ (123 +/- 5 versus 101 +/- 8 mEq/L, p less than 0.05). These data demonstrate that pulsatile flow can significantly attentuate the vasopressin stress response to bypass. Since vasopressin, at these concentrations, is a potent vasoconstrictor and is capable of producing a Na+ diuresis, this may partially explain the higher flow requirements and the decrease in Na+ excretion.

Blood Pressure↗
PubMed1981

Attenuation of the stress response to cardiopulmonary bypass by the addition of pulsatile flow.

The effect of pulsatile flow during cardiopulmonary bypass on the hormonal stress response was studied in 26 patients. Thirteen had routine and 13 had pulsatile bypass with an average pulse pressure of 30 mm Hg. Plasma vasopressin levels were significantly elevated during bypass in both groups, but were lower with pulsation (66 +/- 11 vs 36.3 pg/ml, p less than 0.05). Epinephrine levels increased in both groups during bypass, but were higher after bypass (1179 +/- 448 vs 713 +/- 140 pg/ml, p less than 0.05) and in the recovery room (1428 +/- 428 vs 699 +/- 155 pg/ml, p less than 0.05) in the nonpulsatile group. The same response was noted in the norepinephrine levels (924 +/- 225 vs 465 +/- 90 pg/ml, p less than 0.05; 1015 +/- 491 vs 717 +/- 112 pg/ml, p less than 0.05). There were no significant changes in renin activity in either group, but the increase after cardiopulmonary bypass was greater in the nonpulsatile group (2.0 +/- 0.7 vs 1.36 +/- 0.4 ng/ml/hr, NS). These data suggest that pulsatile flow significantly attenuates the vasopressin and catecholamine stress response to cardiopulmonary bypass. This may explain the increased flow requirements and better tissue perfusion and organ function and the decreased incidence of postoperative hypertension after bypass using pulsatile flow.

Blood Gas Analysis↗
PubMed1981

The effect of pulsatile perfusion on preservation of left ventricular function after aortocoronary bypass grafting.

Pulsatile perfusion has been reported to be of value in intraoperative myocardial protection. To evaluate this technique, we studied 26 patients undergoing aortocoronary bypass grafting. Ejection fraction determinations from multigated cardiac blood pool scans, serial hemodynamic monitoring, and total CPK and MB-CPK sampling were performed early (4, 6 and 8 hours after bypass) and 10 days after operation. In 12 patients, pulsatile perfusion was started immediately after aortic cannulation and continued until 10 minutes after cessation of bypass; 14 patients had standard nonpulsatile perfusion. All patients had a single aortic cross-clamping and potassium cardioplegia. Cross-clamp time (46 +/- 3 and 46 +/- 3 minutes [+/- SEM]), total bypass time (94 +/- 4 and 89 +/- 6 minutes), and mean perfusion pressure (82 +/- 5 and 83 +/- 3 mm Hg) were comparable in the pulsatile and nonpulsatile groups, respectively, as were extent of coronary disease and number of bypass grafts. Preoperative and postoperative ejection fractions for pulsatile and nonpulsatile groups, respectively, were 0.57 +/- 0.03 and 0.55 +/- 0.04 before operation, 0.37 +/- 0.03 and 0.40 +/- 0.04 4 hours after bypass, 0.40 +/- 0.03 and 0.46 +/- 0.04 at 6 hours, 0.51 +/- 0.05 and 0.52 +/- 0.07 at 8 hours and 0.56 +/- 0.05 and 0.53 +/- 0.04) 10 days after operation. Mean arterial pressure, left atrial pressure and serial cardiac indexes were similar in both groups. There were no perioperative myocardial infarctions by ECG in either group. Total CPK (586 +/- 78 and 617 +/- 140 IU/l) and peak MB-CPK (73 +/0 14 and 61 +/- 11 IU/l) were comparable in the pulsatile and nonpulsatile groups, respectively. Pulsatile perfusion offers no advantage in myocardial preservation after aortocoronary bypass grafting in patients with normal left ventricular function.

Coronary Artery Bypass↗
PubMed1981

Hemodynamic and clinical evaluation of the Hancock modified-orifice aortic bioprosthesis.

Clinical experience with the Hancock porcine bioprosthetic heart valve was reviewed in 150 consecutive patients (82 men and 69 women), 13-83 years of age (mean 65 years and 65% older than 60 years), who underwent aortic valve replacement from February 1977 to December 1979. Thirty-eight percent of the patients had associated procedures, including aortocoronary bypass grafting (CABG), valvuloplasty and multiple valve replacement. Overall early mortality was 5% (eight of 150 patients): three of 98 who had isolated aortic valve replacement (AVR), two of 21 who had aortic and mitral valve replacement (AVR/MVR), one of 26 who had AVR/CABG and two four who had AVR/MVR/CABG. In a follow-up period of 6-42 months (mean 26 months), 10 patients have died. Predicted 3-year survival for the study population was 80%. Ninety percent of surviving patients in New York Heart Association functional class I. Incidence of emboli has been 1.5/100 patient-years. Of the five cases of endocarditis, three were fatal and all required reoperation. There have been no primary valve failures. In 43 patients, transvalvular intraoperative peak systolic gradients (left ventricular to aorta) were measured. In those with 19-mm valves (two patients), the gradient was 12.5 +/- 3.5 mm Hg; in those with 21-mm valves (16 patients), it was 10.0 +/- 6.5 mm Hg; in those with 23-mm valves (18 patients), it was 10.8 +/- 5.9 mm Hg; and in those with 25-mm valves (seven patients), it was 9.8 +/- 5.8 mm Hg. Thus, the Hancock modified orifice valve has good hydraulic performance and a low embolic rate without the need for anticoagulation, so it is acceptable for the elderly patient with a small aortic root.

Adolescent↗
PubMed1981

Hemodynamic evaluation of Hancock and Carpentier-Edwards bioprostheses.

The Hancock (H) and Carpentier-Edwards (CE) porcine xenografts are the most commonly used bioprostheses hemodynamic performance of these valves at each valve size was assessed by intraoperative measurement of transvalvular gradients and cardiac outputs in 122 patients undergoing aortic or mitral valve replacement. At comparable cardiac outputs, peak aortic valve gradients (+/- DS) were: 23-mm valve - H (modified orifice) 10.8 +/- 5.9 mm Hg, CE 7.6 +/- 6.2 mm Hg; 25-mm valve - H 11.9 +/- 5.5 mm Hg, CE 8.3 +/- 5.9 mm Hg; 27/29-mm valve - H 11.0 +/- 6.0 mm Hg, CE 6.6 +/- 5.0 mm Hg. Mitral valve gradients were: 29-mm valve - H 3.7 +/- 1.2 mm Hg, CE 2.8 +/- 1.1 mm Hg; 31-mm valve - H 3.5 +/- 1.0 mm Hg, CE 2.6 +/- 0.7 mm Hg, 33/35-mm valve - H 3.2 +/- 1.9 mm Hg. In both the mitral and aortic positions, Carpentier-Edwards porcine bioprostheses had significantly lower (p less than 0.01 and P less than 0.05, respectively) transvalvular gradients than Hancock porcine xenografts.

Aortic Valve↗
PubMed1980

Extended evaluation of effects of anoxia on ventricular performance and compliance.

Eight dogs were prepared by implanting a left ventricular pressure transducer, aortic flow probe, and endocardial ultrasound crystals across the maximum transverse left ventricular diameter. In an unanesthetized state, the dogs were evaluated at rest and with acute volume loading, both before ischemic cardiac arrest and sequentially (2, 4, 6, 12, 24, and 48 hours) after 20 minutes of arrest during normothermic cardiopulmonary bypass. At a left ventricular end-diastolic diameter comparable to preoperative levels, left ventricular systolic pressure, heart rate, and rate of rise of left ventricular pressure were not changed, but at 2 to 6 hours there was a significant decrease in cardiac output (p less than 0.01), left ventricular stroke work (p less than 0.01), ejection fraction (p less than 0.05), maximum rate of systolic diameter shortening (p less than 0.05), and circumferential fiber shortening (p less than 0.05). They gradually returned to control levels by 24 hours postoperatively. Left ventricular compliance, as measured by left ventricular end-diastolic pressure at a set end-diastolic diameter and by left ventricular diastolic pressure/diameter, was reduced at 2 hours (p less than 0.01) and gradually returned to control values at 48 hours. Thus, reversible myocardial injury due to anoxia is associated with both decreased contractility and compliance, with resultant depressed left ventricular performance for 24 to 48 hours after injury.

Animals↗
PubMed1980

Development of seamless tri-leaflet valves.

In terms of their hydrodynamic characteristics at physiologically-relevant flows, the tri-leaflet valves show remarkable in vitro performance in comparison with similarly sized or even larger prosthetic valves. The ongoing in vivo studies confirmed the importance of adequate fluid mechanical design criteria, surface smoothness and rigorously clean fabrication procedures to minimize thrombo-embolic phenomena in the absence of anticoagulant therapies. Results from ongoing in vitro and in vivo durability studies suggest these are promising prostheses for valve replacement.

Animals↗
PubMed1980

Myocardial protection with hypothermia and potassium cardioplegia during operation for ascending aortic aneurysms.

The operative management of aneurysms of the ascending aorta continues to present a technical challenge to the surgeon, and the results obtained provide a useful clinical assessment of the means of myocardial protection. We present a series of 35 consecutive patients who underwent operations for aneurysms of the ascending aorta during which myocardial protection was achieved with hypothermia and potassium cardioplegia. Twenty-three patients underwent aortic valve replacement and resection and grafting of a chronic ascending aortic aneurysm. Aortic valve replacement and aneurysmorrhaphy of a chronic ascending aneurysm were performed in five patients. Four patients underwent resection and grafting of a chronic ascending aortic aneurysm and three patients resection and grafting of acute aortic aneurysms. Aortic cross-clamp times varied from 48 minutes to 2 hours, 32 minutes, with a mean cross-clamp time of 1 hour, 29 minutes. There was one death in the hospital in this series of 35 patients for a mortality rate of 2.8%. Of the 34 survivors, there has been one late death from recurrent sternal wound infection. This clinical series documents the efficacy and safety of hypothermic potassium cardioplegia for protection of the myocardium during extended periods of ischemia attending operative correction of ascending aortic aneurysms.

Adolescent↗
PubMed1979

Medically refractory unstable angina pectoris. I. Long-term follow-up of patients undergoing intraaortic balloon counterpulsation and operation.

Of 82 patients with medically refractory unstable angina pectoris seen between October 1972 and January 1978, 60 patients underwent a combination of intraaortic balloon pump counterpulsation, cardiac catheterization and coronary revascularization. Most patients had atherosclerotic involvement of the vessels of the anterior left ventricular wall, 48 patients (80 percent) had abnormalities of left ventricular wall contraction and 22 patients (36 percent) had evidence of acute myocardial injury. One operative and one late death occurred. The perioperative infarction rate was 5 percent. Survivors, followed up for 3 to 63 months (mean 31 months), have done remarkably well; 77 percent are considered employable,and more than 90 percent are in functional class I or II.

Angina Pectoris↗