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Biomedical subjects

S Levitsky

Publications and source records attributed to S Levitsky.

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

Failure of surgery in preexcitation. Correlation with pathologic findings.

A 37-year-old man with mitral stenosis and recurrent drug-resistant paroxysmal atrial fibrillation, paroxysmal supraventricular tachycardia, and preexcitation, underwent two surgical attempts to ablate an anomalous pathway (AP). Electrophysiologic study demonstrated a left posterior AP with a short antegrade refractory period. Epicardial mapping at the time of mitral valve replacement (left lateral thoracotomy) suggested a posterior right AP. Mitral valve replacement and incision of the left atrial wall failed to cure preexcitation. Epicardial mapping at a second operation (median sternotomy) demonstrated a subepicardial left posterior AP. Right atrial and atrial septal incisions failed to cure preexcitation. Serial section of the atrioventricular rings and conduction system demonstrated an intact left posterior anomalous atrioventricular muscle bundle with surgical incision placed above the plane of the mitral anulus.

Adult↗
PubMed1978

Self-initiated conversion of paroxysmal atrial flutter utilizing a radio-frequency pacemaker.

A patient is described with drug-resistant recurrent paroxysmal atrial flutter. Electrophysiologic studies demonstrated that flutter was inducible with rapid atrial stimulation (stimulation rates of 375 to 400/min) and convertible with rapid atrial stimulation (rates of 400 to 460/min). Because of the latter response, a radio-frequency atrial pacemaker was implanted, which allowed self-initiated conversion of flutter episodes with rapid stimulation.

Arrhythmias, Cardiac↗
PubMed1978

Potassium cardioplegia. An alternate method of intraoperative myocardial protection.

Potassium-induced cardioplegia was studied in 38 mongrel dogs supported by normothermic cardiopulmonary bypass and subjected to 60 minutes of aortic cross clamping followed by 30 minutes of reperfusion. A study of preischemic and postischemic ventricular function and myocardial high-energy phosphate compounds, lactate, and glycogen showed substantial preservation of high-energy phosphates and ventricular performance when potassium cardioplegia was used. However, the substantial depression in contractility observed following ischemia nad reperfusion suggests that potassium cardioplegia alone does not provide adequate intraoperative protection of the myocardium.

Adenosine Diphosphate↗
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

Intraoperative protection of the myocardium.

It appears obvious that in evaluating gross mortality and morbidity, clinical statistics are insufficient to demonstrate which form of a myocardial protective measure is safest. Previous studies indicate that significant ischemic injury may not be detectable by routine measurements of contractility. Only microscopic examination of the heart at a later period will allow detection of the patchy ischemic injury. In patients, loss of cardiac reserve as measured by postoperative catheterization, particularly compliance studies, and stress testing may be the final clinical arbiter of this controversy.

Aorta↗
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

Does intermittent coronary perfusion offer greater myocardial protection than continuous aortic cross-clamping?

There has been considerable controversy concerning the relative merits of intermittent coronary perfusion vs. continuous aortic cross-clamping for cardiac procedures requiring ischemic arrest. Using the isovolumic ventricular balloon model and "stop-freeze" biopsy techniques, myocardial contractility (LV dp/dt max, length-tension, and force-velocity relationships) and metabolism (adenine nucleotides, creatine phosphate, and glycogen) were studied in 46 intact dogs supported by normothermic cardiopulmonary bypass and subjected to either 60 minutes of continuous ischemic arrest or to four 15-minute intervals of ischemia each followed by 5 minutes of reperfusion. Following ischemia the hearts were reperfused for 30 minutes and defibrillated after the first 10 minutes. There were no significant differences in either metabolic parameters or contractile function between the groups. Although partial regeneration of adenosine triphosphate and glycogen occurred during reperfusion, only creatine phosphate achieved normal values and the end result was no difference between the two techniques. These data indicate that 5 minutes of coronary reperfusion between consecutive episodes of ischemic arrest affords no greater intraoperative protection of the myocardium than does continuous aortic cross-clamping.

Adenine Nucleotides↗
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↗