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Biomedical subjects

S Levitsky

Publications and source records attributed to S Levitsky.

At least 145 records · Page 8Linked to original sources
PubMed1984

Etiology of atrioventricular-conduction abnormalities following cardiac surgery.

Atrioventricular-nodal-conduction abnormalities following cardiac surgery have been attributed to the potassium ion in cardioplegic solutions. To clarify the etiology of these rhythm problems, 15 dogs were subjected to (I) 60 min 4 degrees C potassium cardioplegic arrest; (II) 30 min normothermic ischemic arrest; or (III) cardiac hypothermia without ischemia. In sinus rhythm and during atrial pacing, A-H and H-V intervals, Wenckebach cycle length (WCL), atrial- and AV-nodal refractory periods (ARP and NRP) were measured at 37 degrees C before and 30 min after arrest (groups I and II) and at various myocardial temperatures (group III). Following cardioplegic arrest and reperfusion, all AV-nodal-conduction properties were unchanged from preischemic values. In contrast, unprotected ischemia significantly prolonged AV-nodal-conduction time (P less than 0.01) and myocardial hypothermia resulted in prolonged WCL (P less than 0.01), prolonged functional NRP (P less than 0.05), in addition to delayed A-H interval (P less than 0.05). The data suggest that properties of AV-nodal conduction are preserved following potassium cardioplegic arrest, but impaired by ischemic injury or persistent local cardiac hypothermia.

Animals↗
PubMed1984

A model of cyanotic heart disease: functional, pathological, and metabolic sequelae in the immature canine heart.

To assess the etiology of depressed ventricular function in cyanotic congenital heart disease, an experimental model in immature puppies was devised in which the left atrial appendage is directly anastamosed to the distally banded pulmonary artery. The preparation results in significant cyanosis during a 3-month study period (PO2 = 91 +/- 4 vs 43 +/- 3, hematocrit = 33 +/- 3 vs 55 +/- 5). Compared to age- and weight-matched unoperated controls, cyanotic animals developed significant depression of biventricular ejection fraction (P less than 0.05), increased heart weight indexed for body weight (P less than 0.05), increased right ventricular weight (P less than 0.02), and increased right ventricular free wall thickness (P less than 0.05). There was no alteration in ventricular volumes. In addition, mean myocardial stores of high-energy phosphate compounds were unaltered. The model allows a reproducible level of hypoxemia to be produced in young animals, utilizes no prosthetic materials, and allows future experiments to be performed to ascertain the metabolic response of the cyanotic myocardium to exercise or surgically induced ischemia.

Animals↗
PubMed1984

Chronic hypoxemia depresses global ventricular function and predisposes to the depletion of high-energy phosphates during cardioplegic arrest: implications for surgical repair of cyanotic congenital heart defects.

Persistence of impaired ventricular function after repair of cyanotic congenital heart defects may be due to previous exposure to chronic hypoxemia or to perioperative ischemic injury. Clarification of this phenomenon was sought in a canine model of cyanotic cardiovascular disease (Group I), in which the left atrium was anastomosed proximal to the banded pulmonary artery. Animals that had pulmonary artery banding alone (Group II) or no prior surgical intervention (Group III) served as controls. All Group I animals became cyanotic during the study period (arterial oxygen tension, 38 +/- 4 mm Hg; hematocrit, 55 +/- 5%). Radionuclide-determined ejection fractions performed three months after operation showed significant depression of global biventricular function by 16 to 29% (p less than 0.05) compared with groups II and III. On cardiopulmonary bypass, all hearts were subjected to 4 degrees C potassium cardioplegic arrest and reperfusion with serial assays for myocardial adenosine triphosphate (ATP) and creatine phosphate (CP) levels. The ATP and CP stores in each ventricle were similar at all sampling intervals, and preischemic levels were comparable in cyanotic and control groups. However, ATP levels were significantly depressed 37 to 43% from preischemic levels (p less than 0.02) after arrest and reperfusion in cyanotic dogs, but they were preserved in Groups II and III. During ischemia, CP stores were depleted to 27% of preischemic values in Group I but only to 46 to 63% of preischemic levels in the control groups (p less than 0.05). These data indicate that chronic hypoxemia impairs global ventricular function and predisposes to the accelerated depletion of high-energy phosphates during cardioplegic arrest.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1984

Acute endocarditis in drug addicts: surgical treatment for multiple valve infection.

In 72 drug abusers surgically treated for acute infective endocarditis, 14 patients (19%) required surgical procedures on two valves. The predominant infecting organisms were Staphylococcus aureus and Pseudomonas aeruginosa (29%). In contrast to single valve infection, congestive heart failure was the most common operative indication (86%, p less than 0.05) and was uniformly present when both left-sided valves were involved. Surgery was performed 20 +/- 13 days after initiation of antibiotic therapy, yet 7 of the 14 patients had perivalvular abscess formation. In nine patients with solely left-sided infection, aortic and mitral valve replacements were performed. In five patients with bilateral infection, partial or complete tricuspid valvectomy was performed in conjunction with one aortic and four mitral valve replacements. Tricuspid valve competence was reestablished by valve insertion or anuloplasty in two patients, and these patients experienced less perioperative heart failure than did those with tricuspid excision alone. There was no early (less than 30 day) mortality. However, long-term follow-up revealed a reoperative incidence of 21% and a 36% late mortality rate due to prosthetic valve infection with or without dehiscence at 3 to 18 months (mean 7.2 +/- 6) after the initial operation. These late infectious complications were not related to infecting organism or prosthetic material in the tricuspid anulus, but did occur in four (57%) of seven patients with intracardiac abscess. The data indicate that multiple valve infection does not preclude successful early surgical therapy, maintaining tricuspid competence may be hemodynamically preferable, and reinfection in this addict population increases late mortality.

Adult↗
PubMed1984

Optimal intraoperative protection of myocardium distal to coronary stenoses.

Metabolic evidence of improved delivery of cardioplegic solutions by adjuvant use of nitroglycerin (NTG) and reinfusing these solutions distal to an obstructed coronary artery was sought in 40 dogs subjected to cold cardioplegic arrest. The left anterior descending coronary artery was occluded prior to initiating arrest by intra-aortic root infusion. Cardioplegic solution was reinfused with the left anterior descending occluded throughout ischemia (Group I), or with this artery reopened, to simulate a completed distal anastomosis (Group II). Serial biopsy specimens of the left ventricular apex were assayed for adenosine triphosphate and creatine phosphate, while specimens from the posterior left ventricular wall served as controls. Regional myocardial temperatures were recorded throughout ischemia. Half of the hearts in each group received 300 micrograms of nitroglycerin in the cardioplegic solution. Adenosine triphosphate was preserved in myocardium distal to a patent coronary artery whether nitroglycerin was added to the cardioplegic solution or not (control, control + NTG). Moreover, nitroglycerin did not prevent the 26% to 34% (p less than 0.05) decline in adenosine triphosphate levels when the left anterior descending remained obstructed throughout ischemia (Group I, I + NTG). However, opening the left anterior descending for reinfusion of cardioplegic solution allowed adenosine triphosphate to be preserved at end-ischemia (Group II, II + NTG). In addition, the metabolic reperfusion injury manifested by a 37% (p less than 0.01) decline in adenosine triphosphate levels after aortic unclamping (Group II) was obviated when nitroglycerin was added to the cardioplegic solution delivered in this manner (II + NTG). The depletion of cardioplegic solution stores during ischemia was more severe in the experimental groups than in controls (p less than 0.05). These metabolic changes did not correlate with regional myocardial temperature gradients. The data indicate that myocardium jeopardized by coronary stenoses can be preserved as well as myocardium supplied by a patent coronary artery by adjuvant use of nitroglycerin and varying the mode of delivery of the cardioplegic solution.

Adenosine Triphosphate↗
PubMed1983

Chlorpromazine inhibits loss of contractile function, compliance and ATP in ischemic rabbit heart.

Using a modified Langendorff preparation, rabbit hearts were either continuously perfused at 37 degrees C for 150 min, in the presence of O2 and substrate, or after a 30 min equilibration period exposed to global ischemia followed by 30 min of reperfusion. Ischemia, for 90 min at 27 decrees C or for 60 min at 37 degrees C was compared. Perfusion pressure, heart rate, and ventricular volume were maintained constant. Contractile function and metabolic status were assessed. The effect of chlorpromazine, administered (30 mg/kg IP) 30 min prior to sacrifice, was compared to the untreated animal. (1) Chlorpromazine had little effect on the contractile function or metabolic status of hearts continuously perfused for 150 min in the presence of O2 and substrate. (2) The chloropromazine-treated hearts maintained contractile function and metabolic status at preischemic levels following exposure to 90 min of global ischemia at 27 degrees C and reperfusion at 37 degrees C. Untreated hearts exhibited a severe deterioration in both contractile and metabolic parameters under the same conditions. Both untreated and chlorpromazine-treated hearts exhibited loss of contractile function after 60 min ischemia at 37 degrees C; untreated hearts had undetectable ATP levels while chlorpromazine-treated hearts exhibited low levels of ATP. (3) Untreated hearts, exposed to 90 min of ischemia at 27 degrees C, exhibited a significant loss in compliance, while the compliance of chlorpromazine-treated hearts was unchanged from pre-ischemic levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1983

Prevention and reperfusion injury following cardioplegic arrest by pulsatile flow.

To assess the efficacy of pulsatile flow in minimizing reperfusion injury following cardioplegic arrest, 20 dogs supported by cardiopulmonary bypass underwent 60 minutes of hypothermic, hyperkalemic crystalloid cardioplegic arrest. The effects of pulsatile flow (Group 2), initiated during 30 minutes of reperfusion, on myocardial adenosine triphosphate (ATP) and creatine phosphate (CP) stores, coronary blood flow, and myocardial water content were compared with the effects of linear flow reperfusion (Group 1). Myocardial ATP stores were maintained at preischemic levels by this mode of myocardial protection. However, pulsatile flow prevented the significant decline in ATP levels incurred during linear reperfusion. Creatine phosphate stores, although depleted during arrest, were restored equally, regardless of the mode of reperfusion. The decline in ATP stores was associated with no pathological increase in myocardial water content, but was associated with persistent reactive hyperemia. In contrast, after 30 minutes of pulsatile reperfusion, coronary blood flow was significantly decreased compared with preischemic flow. These data indicate that pulsatile reperfusion can prevent the unique decline in ATP levels associated with the restoration of coronary flow after cardioplegic arrest (reperfusion injury), and support its continuing evaluation as an adjunct to adequate intraoperative myocardial protection.

Adenosine Triphosphate↗
PubMed1983

Valve replacement for left-sided endocarditis in drug addicts.

Eighteen drug addicts with left-sided valvular endocarditis requiring operation are reviewed. Gram-positive bacteria were the most common organisms cultured (61%), with Staphylococcus aureus present in 7 of 11 patients. Gram-negative bacteria, exclusively Pseudomonas aeruginosa, were cultured in the remaining 39%. Indications for operation included sepsis (61%), heart failure (78%), and systemic emboli (22%). Abscesses formed in 6 of 11 patients with gram-positive endocarditis, while only one abscess was present with gram-negative endocarditis. Normal valves were infected in 17 of 18 patients (94%). Early surgical mortality (less than 30 days) was 11%. There were major complications in 79% of these patients, including persistent sepsis (50%), valvular dehiscence, prosthetic endocarditis or perivalvular leakage (37%), and mycotic aneurysms (22%). These complications were directly related to a late mortality of 44%, yielding an overall mortality of 50% in the first nine months after operation. Contrary to previous reports of acceptable surgical survival for valvular endocarditis, these data suggest that endocarditis involving the aortic or mitral valve in a drug addict is a highly lethal disease due to the virulence of the organisms, the severity of the complications encountered, and the predisposition to continued addiction.

Adolescent↗
PubMed1983

Beneficial metabolic effect of nucleoside augmentation on reperfusion injury following cardioplegic arrest.

Restoration of coronary flow after hyperkalemic cardioplegic arrest (HCA) is associated with a unique metabolic reperfusion injury (RI) manifested by declining nucleotide stores despite their end-ischemic preservation. Prevention of this RI by exogenous provision of adenosine with or without inhibition of adenosine's major catabolic enzyme was assessed in 27 dogs subjected to 60 minutes of HCA. The effect of aortic root infusion of 40 mg/kg of adenosine in addition to adenosine deaminase inhibition by 10 mg/kg of EHNA (group 2) initiated during 60 minutes of reperfusion on myocardial adenosine triphosphate (ATP) and creatine phosphate (CP) stores and coronary blood flow (CBF) were compared to animals having adenosine infusion alone (group 3) or controls (group 1). Although ATP levels were preserved at the end of HCA in all groups, adenosine infusion with or without EHNA prevented the significant 23 percent decline in ATP stores incurred during unmodified reperfusion (p less than 0.01, group 1). The CP stores decreased (p less than 0.05, all groups) during arrest, but were restored to preischemic levels during reperfusion. When measured 60 minutes after aortic unclamping, CBF was 312 percent of preischemic flow in group 3 (p less than 0.01), only 170 percent in group 2 (p less than 0.05), and unchanged in controls (group 1). The data indicate that provision of adenosine as a nucleotide precursor prevents the metabolic RI following HCA. In addition, inhibition of adenosine catabolism is not necessary for this salutary effect, nor is adenosine's efficacy solely mediated by augmentation of CBF.

Adenine↗
PubMed1983

Induction of cardioplegia with blood and crystalloid potassium solutions during prolonged aortic cross-clamping.

Recent controversy concerns the proper vehicle for delivery of potassium cardioplegia. In the present study, adult dogs supported by cardiopulmonary bypass were subjected to 2 hours of multidose, hypothermic potassium cardioplegic arrest with 30 minutes of reperfusion with either autologous blood or crystalloid solution as the cardioplegic vehicle. Preservation of myocardial high-energy nucleotide stores was assessed by serial left ventricular biopsies assayed for adenosine triphosphate (ATP) and creatine phosphate. Preischemic and postischemic ventricular function was assessed by the use of an isovolumic intraventricular balloon. ATP stores were equally maintained at preischemic levels after ischemia and reperfusion by both autologous blood and crystalloid solution. Although creatine phosphate stores significantly declined (P less than 0.01, both groups) after 2 hours of arrest, reperfusion allowed equal restoration of preischemic levels. Maximum first derivative of left ventricular pressure and measured velocity were not depressed by either mode of protection. Similarly, myocardial compliance, as assessed by length-tension curves, showed no change following either autologous blood or crystalloid solution. The data show equal and significant myocardial protection by multidose, hypothermic potassium cardioplegia when both delivery vehicles were used.

Animals↗
PubMed1983

Cardioplegia does not prevent reperfusion injury induced by intracoronary platelet deposition.

We have shown that after global myocardial ischemia, reperfusion injury may be related to platelet deposition in the coronary microcirculation. The purpose of this study was to determine whether multidose hypothermic potassium cardioplegia suppresses platelet deposition during postischemic reperfusion. Platelets labeled with 111In and erythrocytes labeled with 51Cr were injected into dogs subjected to either 120 min of continuous cardiopulmonary bypass (control, n = 4), 60 min of global normothermic myocardial ischemia followed by 50 min of reperfusion (n = 6), or global ischemia with cardioplegia (n = 5). Intracoronary platelet deposition was determined by comparing the double-labeled isotope activity of myocardial biopsy specimens to peripheral blood. Reperfusion after global myocardial ischemia resulted in substantial deposition of platelets within the coronary vasculature in both the cardioplegia-treated (215 +/- 40 platelets/mg) and untreated (269 +/- 95 platelets/mg) groups. These increases were significantly greater than those measured during continuous bypass (48 +/- 2 platelets/mg; p less than .01). Cardioplegia, despite apparent washout of the microcirculation, does not alter platelet deposition. Thus other platelet-stabilizing measures must be used to prevent platelet deposition-induced reperfusion injury after surgical global ischemia.

Animals↗
PubMed1983

Efficacy of pulmonary artery banding in infants with complete atrioventricular canal.

Total correction in infants less than 1 year old with complete atrioventricular (AV) canal carries a significant operative mortality. However, past reports suggest that the alternative palliative procedure, pulmonary artery banding (PAB), may be contraindicated in the presence of severe mitral insufficiency and/or a large left ventricular to right atrial shunt. Contrary to these previous reports, we report the results in 21 consecutive patients with congestive heart failure who underwent PAB at a mean age of 3.9 +/- 2.8 months and at a weight of 3.6 +/- 0.9 kg. (17/21 less than 6 months). Regardless of mitral valve competency, PAB was performed in conjunction with ligation of a patent ductus arteriosus (11 patients) and coarctation repair (two patients) with one death secondary to gastrointestinal bleeding (4.7% in-hospital mortality); one patient required early band readjustment because of hypoxemia. Repeat cardiac catheterization in 10 patients performed 4 to 41 months after PAB showed significant reduction in pulmonary hypertension and flow with no change in pulmonary vascular resistance. All infants were symptomatically improved after PAB and four have undergone successful total correction. Previous reports since 1977 indicate a significantly higher risk for total repair of complete A V canal before 1 year of age (36/147, 24%) than the risk for PAB in this series (p less than .05). Therefore, we believe that PAB is a rational alternative to total repair as the initial surgical treatment for symptomatic infants with complete A V canal, particularly when anatomic variants known to increase operative risk are recognized before cardiotomy.

Cardiac Catheterization↗
PubMed1982

Prostaglandin E1 infusion in newborns with hypoplastic left ventricle and aortic atresia.

Prostaglandin E1 (PGE1) infusion was used in 7 infants with hypoplastic left ventricle and aortic atresia. Of 5 non-operated patients, 4 died shortly after the onset of PGE1 infusion and 1 survived for 30 hours. Of the infants who had surgery, 1 died during the operation and 1 survived for 38 days. In 6 infants, a transient metabolic and/or circulatory improvement could be demonstrated following PGE1 infusion. The lack of response of other infants may be related to the advanced deterioration of their clinical status at the time of study. In the light of recent surgical developments for infants with aortic atresia, support with PGE1 may nevertheless play an important role in their management if started early.

Abnormalities, Multiple↗
PubMed1982

Efficacy of low-dose propranolol in preventing postoperative supraventricular tachyarrhythmias: a prospective, randomized study.

A prospective, randomized study was performed in 100 consecutive patients undergoing coronary artery bypass surgery to assess the efficacy of the early reinstitution of propranolol in reducing the incidence of postoperative supraventricular tachyarrhythmias (SVT). Patients were randomized to receive propranolol 10 mg every 6 hours enterally starting the morning after surgery (Group I, 50 patients) or to serve as controls (Group II, 50 patients). No patient was excluded because of poor ventricular function, need for urgent revascularization, or transient necessity for ionotropic support. Both groups had a comparable incidence of risk factors, previous infarction, unstable angina, and abnormal ventricular function. The extent of coronary disease, preoperative propranolol dose, and number of grafts performed were also similar. SVT occurred in 3/50 (6%) patients in Group I compared with 14/50 (28%) in Group II (p less than 0.01). There were no preoperative or intraoperative discriminators to predict the occurrence of SVT. In addition, perioperative infarction and the need for mechanical or pharmacologic circulatory support did not predispose to SVT. The data indicate that early administration of propranolol should be given to all patients after myocardial revascularization to decrease the incidence of these postoperative rhythm disturbances.

Arrhythmias, Cardiac↗
PubMed1982

Postoperative electrophysiological studies with a modified radiofrequency system. Technical aspects and clinical usefulness.

Two patients who underwent a ventricular aneurysmectomy for treatment of ventricular tachycardia are presented. In both patients, a radiofrequency pacemaker was implanted at surgery (for therapeutic use if surgery should fail). In both patients, electrophysiological studies were performed before discharge utilizing a radiofrequency pacemaker without recourse to repeat catheterization. This was possible by modifying the transmitter and coupling it to a commercially available programmable stimulator.

Electrocardiography↗