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Biomedical subjects

R M Engelman

Publications and source records attributed to R M Engelman.

At least 181 records · Page 10Linked to original sources
PubMed1979

Epicardial activation of the intact human heart without conduction defect.

To describe the epicardial ventricular activation sequence in the intact human heart, we obtained epicardial maps from 11 patients with normal QRS undergoing open heart surgery. Epicardial breakthrough (EBT), defined as the emergence of a radially propagating epicardial wavefront, occurred in three to five sites in each patient, and was earliest in the anterior right ventricle, 7--25 msec (mean 17 msec) after the onset of the QRS in all patients. Subsequent EBT occurred in the inferior right ventricle (10 sites in 10 patients), in the anterolateral left ventricle (13 sites in 10 patients), and the inferior left ventricle (eight sites in seven patients). Latest epicardial activation (LEA), defined as the latest site of recordable epicardial activity, occurred in the basal segments in all patients, anteriorly in the right ventricle in five patients, and inferiorly in six patients, four on the right and two on the left. LEA occurred 63--96 msec (mean 77 msec) after the onset of the QRS, and was recorded within 20 msec of the end of the QRS in all patients. Sequence of epicardial activation reflected a fusion process among the wavefronts. This descriptive and quantitative data should provide a suitable basis for comparison of abnormal ventricular activation sequences in patients undergoing surgery for preexcitation or ventricular tachycardia.

Adult↗
PubMed1979

New technique for repair of posterior left ventricular rupture.

A case is presented of posterior left ventricular rupture occurring from resection of intramyocardial calcification during mitral valve replacement. The laceration was obvious on the operating table with discontinuation of cardiopulmonary bypass, but attempts at simple closure with buttressd sutures were unsuccessful. The ventricular defect was repaired by insertion of a low-porosity Dacron graft. A saphenous vein bypass graft was also placed between the aorta and circumflex coronary artery.

Heart Rupture↗
PubMed1979

The time course of myocardial high-energy phosphate degradation during potassium cardioplegic arrest.

Myocardial high-energy phosphate and glucose-6-phosphate levels were determined in the in vivo pig heart model during ischemic arrest and reperfusion to determine the effectiveness of potassium cardioplegia in myocardial protection. Thirty-five pigs were divided into six experimental groups consisting of 2-hour normothermic arrest, 2-hour hypothemic arrest, 2-hour normothermic cardioplegic arrest, and 1-, 2-, and 3-hour hypothermic cardioplegic arrest. Myocardial biopsies from the left ventricle were obtained prior to arrest, every 30 minutes during the arrest interval, and at 30 and 60 minutes of reperfusion. The measurement of adenosine triphosphate and creatine phosphate showed that (1) cardioplegic arrest requires hypothermia to preserve high-energy phosphate levels in myocardial tissue; (2) hypothermia, while not completely protective alone, is more effective than potassium cardioplegia alone in providing myocardial preservation during 2-hour ischemic arrest; (3) the combination of potassium cardioplegia and hypothermia is additive in providing an effective means of maintaining myocardial high-energy phosphate stores during 1, 2, and 3 hours of ischemic arrest; (4) myocardial reperfusion does not allow a return to preischemic adenosine triphosphate (ATP) levels after 2 hours of arrest, except following hypothermic cardioplegia; and (5) extension of the duration of ischemic arrest to 3 hours using hypothermic cardioplegia prevents recovery of high-energy phosphate stores to preischemic levels during reperfusion. Optimal preservation can be achieved during 2 hours of ischemic arrest by using hypothermic potassium cardioplegia. The effects of myocardial reperfusion, however, prevent full ATP and creatine phosphate (CP) recovery following 3 hours of arrest. No other technique studied was as effective in providing myocardial preservation.

Adenosine Triphosphate↗
PubMed1978

Delayed mediastinal infection after ventricular aneurysm resection.

A patient developing delayed mediastinal infection following ventricular aneurysm resection and double coronary bypass is presented. The source of sepsis was infection of a ventriculotomy incision that had been closed with Teflon-felt buttresses. Diagnosis was established by an increasing opacity on the lateral chest roentgenogram with a stable sternal wound. Treatment was ultimately successful only after removal of the infected Teflon and replacement by simple mattress closure. The need to remove the infected foreign body was clearly established by the initially unsuccessful attempt at simple debridement.

Heart Aneurysm↗
PubMed1978

Evaluation of the Hunter-Sessions self-retaining aortic cannula.

A report of our experience with a new self-retaining aortic cannula is presented. We have used this cannula in more than 30 patients and found it to be very secure and convenient for rapid cannulation since no pursestring sutures are required for initial placement.

Adult↗
PubMed1978

Cardioplegia and myocardial preservation during cardiopulmonary bypass.

A standard experimental protocol was developed to explore the role of hypothermia and potassium cardioplegia in myocardial preservation during 120 minutes of ischemic arrest followed by 30 minutes of reperfusion. Seven different experimental groups of six animals each were evaluated using an in-vivo pig heart preparation. Hypothermic arrest without cardioplegia and cardioplegic arrest at normothermia were each compared to hypothermic cardioplegia. In addition, the use of an asanguineous hypothermic coronary perfusate without cardioplegia was compared to both multidose cardioplegia and single-dose cardioplegia followed by the same asanguineous perfusate. The parameters measured included: myocardial contractility and compliance, myocardial blood flow, endocardial/epicardial blood flow ratio, and electron microscopic studies. Myocardial preservation was inadequate with hypothermic arrest alone (without cardioplegia; and with cardioplegia at normothermia. In both experimental groups, myocardial contractility and compliance were so depressed that the) could not be accurately measured following ischemia and reperfusion while coronary blood flow remained significantly elevated. Preservation was improved but still inadequate following myocardial washout with a normokalemic or hypokalemic perfusate and following single dose cardioplegia plus myocardial washout. In the latter four groups, contractility ranged from 42 to 78% of control, and there was a decrease in compliance of 16 to 78%. Adequate preservation was found only after hypothermia and multidose potassium (35 mEq/L) cardioplegia. In this group, contractility was 129 +/- 13% of control and compliance increased by 21 +/- 24% compared to that of the control.

Animals↗
PubMed1978

The significance of multidose cardioplegia and hypothermia in myocardial preservation during ischemic arrest.

A standard experimental protocol was developed to explore the optimal technique for myocardial preservation during 120 minutes of ischemic arrest followed by 30 minutes of reperfusion. Eight different experimental groups were evaluated with the use of an in vivo pig heart preparation. The parameters measured included myocardial contractility and compliance, myocardial blood flow, and endocardial/epicardial blood flow ratio. Myocardial preservation was inadequate after hypothermic arrest alone, cardioplegic arrest alone (at normothermia), and single-dose cardioplegia plus hypothermia. Adequate myocardial preservation was found only after hypothermia and multidose cardioplegia with either potassium (35 mEq. per liter) or magnesium-procaine solutions. Continuous cardioplegia and hypothermia, while providing a moderate degree of myocardial preservation, was not as satisfactory as multidose cardioplegia and hypothermia. No difference in myocardial preservation was apparent when potassium-induced cardioplegia was compared with magnesium-procaine-induced cardioplegia.

Animals↗
PubMed1977

Optimal conditions for reperfusion during cardiopulmonary bypass.

An experiment was designed to determine optimal methods of myocardial reperfusion after normothermic ischemic arrest in the in vivo pig heart. Four variables were studied: 1) ischemic arrest for 15 minutes repeated six times vs 30 minutes repeated three times: 2) coronary reperfusion between each arrest period lasting 5 or greater than or equal to 15 minutes (the latter duration dependent upon electrocardiographic reversal of ischemic); 3) perfusion pressure of 50, 75, or 100 mm Hg; and 4) a beating or fibrillating heart during reperfusion. The effects of perfusion were monitored by measuring the endocardial/epicardial perfusion ratio (with ratioactive microspheres), coronary blood flow, and coronary reactive hyperemia by measuring coronary vascular resistance during reperfusion. Electron micrographs were examined to determine if subtle distinctions between groups could be measured. A total of 78 pigs (60 experimental and 18 control) were evaluated. The experimental animals were divided into 10 groups of six pigs each. In each group only one of the four variables (beating or fibrillating ventricle, perfusion pressure, duration of ischemia, and duration of reperfusion) was altered to provide comparative data. Results are based on improved endocardial perfusion and a greater coronary reactive hyperemic response when comparing each experimental group to one another and to control animals. Reperfusion of a contracting rather than fibrillating ventricle resulted in improved endocardial flow as did reperfusion at a low (50 or 75 mm Hg) rather than a high (100 mm Hg) perfusion pressure. A short ischemic interval repeated six times rather than a longer ischemic interval repeated three times also allowed for improved subendocardial perfusion and a greater reactive hypermic response as did a longer reperfusion period between equal ischemic intervals. Electron microscopic studies showed a gradation of abnormalities ranging from little deviation from control in beating hearts and short ischemia and long duration, low pressure reperfusion to marked mitochondrial vacuolization in fibrillating hearts subjected to long ischemia, short reperfusion at high perfusion pressures. The best technique for myocardial reperfusion based on available data is to provide reperfusion of adequate duration in order to reverse the ischemic electrocardiogram in a beating heart, avoiding an excessively high perfusion pressure.

Animals↗
PubMed1976

Myocardial injury associated with potassium arrest.

The relative efficacy of potassium-induced ischemic arrest using buffered, isosmotic potassium (25 mEq/liter) was compared with hypothermic arrest in an experimental protocol employing an intact canine heart preparation. Myocardial function (LVSW, dp/dt max), serum creatine phosphokinase levels, myocardial perfusion, and light and electron microscopical examination of the heart were assessed in five groups of 5 dogs each. There was one control group (90 minutes of bypass, no anoxia) and four experimental groups, each subjected to 1 hour of ischemic arrest and 30 minutes of reperfusion, comparing normothermic ischemic arrest (NIA), hypothermic ischemic arrest (myocardial temperature less than 25 degrees C) (HIA), normothermic potassium arrest (NKA), and hypothermic potassium arrest (HKA). Myocardial function decreased significantly following NIA and NKA but remained essentially equal in the control, HIA and HKA groups. Serum creatine phosphokinase analysis documented a significant increase in each group of animals: 2,250 mU after NIA, 1,778 mU after NKA, 1,388 mU after HIA, 1,220 mU after HKA, and 838 mU after control bypass. Left ventricular myocardial perfusion was unmeasurably low after NIA, reduced to 111 m/100 gm of tissue/min after NKA, and increased to 165 to 188 ml/100 gm/min in the control, HIA and HKA groups. Electron microscopical studies showed a range of myocardial changes, from probably irreversible damage after NIA to similar but less diffuse changes after NKA, and to potentially reversible changes after HKA and HIA with the least alteration from control after HIA. The results indicate that potassium arrest alone is not as effective as hypothermia in preventing ischemic injury, and the combination of hypothermia with a single 150 cc administration of potassium (25 mEq/liter) does not appear to provide significant additional protection.

Animals↗
PubMed1976

Coronary artery bypass with freeze-preserved saphenous vein allografts.

Over the past 5 years, 13 patients had coronary artery bypass performed with freeze-preserved saphenous vein allografts. There were no operative deaths or significant morbidity. Six patients were studied postoperatively at 42, 37, 10, 7, 5, and 1 months. Six of 8 grafts were patent with good flow. There were four late deaths; two of these occurred in patients who had concomitant resection of a ventricular aneurysm. Of the 9 surviving patients, 6 (6/9) are asymptomatic and 2 (2/9) have occasional chest pains; the condition of 1 patient (1/9) is unchanged. This experience suggests that free-preserved saphenous vein allografts may be used successfully for coronary bypass when autologous veins and internal mammary arteries are unavailable or insufficient for multiple bypass.

Aged↗
PubMed1976

Operative management of tricuspid regurgitation.

From January 1968 to June 1975 tricuspid regurgitation was encountered in 238 patients of a total of 1074 patients undergoing operations on the mitral valve. During this time tricuspid annuloplasty (TA) was performed in 137 patients and the tricuspid valve was replaced (TVR) in 101 patients. Comparison of hospital mortality of 15% (20 of 137) for TA as against 40% (40 or 101) for TVR suggests the superiority of repair over replacement. A new technique for repair makes this operation even more attractive. It satisfies the dual objectives of producing competency but not obstruction by creating a measured orifice. As experience with TA was gained, the incidence of valve replacement dropped from 69% (22 of 32) in the first 2 years of the study to 16% (11 of 70) for the last 2 years.

Adult↗