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Biomedical subjects

W R Lewis

Publications and source records attributed to W R Lewis.

At least 37 records · Page 2Linked to original sources
PubMed1995

Advantages of continuous noncardioplegic warm blood retrograde perfusion over antegrade perfusion during proximal coronary anastomoses.

Retrograde perfusion via the coronary sinus supplies vascular beds distal to coronary stenoses and has been used for administration of cardioplegia. An additional application is to supply noncardioplegic retrograde perfusion while performing proximal anastomoses (a time when cardiac arrest is not critical). The aim of this study was to determine the safety of this technique and to study the metabolic changes with antegrade versus retrograde warm blood perfusion. Sixty-six patients, with good left ventricular function, underwent distal coronary bypass in a similar fashion. Proximal anastomoses were done with 1) partial occlusion clamp (n = 29) or 2) cross-clamp on and continuous, warm, noncardioplegic retrograde blood perfusion (n = 37). In an additional 10 patients, metabolism was assessed with antegrade and retrograde perfusion during proximal anastomoses. Despite longer cross-clamp times (96.4 +/- 6.2 vs 80.8 +/- 3.1 min, p < 0.05) with retrograde perfusion, the total duration of cardiopulmonary bypass was significantly less (119.6 +/- 6.2 vs 136.6 +/- 4.6 min, p < 0.05). There was superior postbypass, intraoperative hemodynamics (cardiac index) with retrograde perfusion (4.0 +/- 0.2 vs 3.6 +/- 0.1 L/min/m2). The incidence of postoperative dysrhythmia was not significantly different between groups. Oxygen and glucose utilization was more efficient with retrograde perfusion. Retrograde perfusion during proximal anastomoses is a safe technique. There is diminished risk of aortic dissection, atheroembolism, delayed aneurysm formation, or rupture due to avoidance of application of partial occlusion clamps. There is evidence of superior substrate utilization.

Aged↗
PubMed1994

Utility and safety of immediate exercise testing of low-risk patients admitted to the hospital for suspected acute myocardial infarction.

More than 2 million patients are admitted to U.S. hospitals annually for clinical suspicion of acute myocardial infarction (AMI), and > 70% are found not to have had a cardiac event. This study evaluates the safety and efficacy of immediate exercise testing for patients admitted to the hospital for suspected AMI. Ninety-three nonconsecutive low-risk patients admitted to the hospital from the emergency department to rule out AMI underwent exercise treadmill testing using a modified Bruce protocol immediately on admission to the hospital (median time < 1 hour). Twelve patients had positive exercise electrocardiograms, 6 of whom had significant coronary narrowing by angiography. An uncomplicated non-Q-wave AMI was diagnosed in 1 patient. Fifty-nine patients had negative and 22 patients had nondiagnostic exercise electrocardiograms. Of these 81 patients, 44 were discharged immediately after exercise testing, 17 were discharged within 24 hours, and 20 were discharged after 24 hours of observation. There were no complications from exercise testing. There were 2 late noncardiac deaths and 1 late AMI. Thus, immediate exercise testing of low-risk patients with chest pain who are at sufficient risk to be designated for hospital admission is effective in further stratifying this group into those who can be safely discharged immediately and those who require hospitalization.

Adult↗
PubMed1994

Intravenous diltiazem for the treatment of patients with atrial fibrillation or flutter and moderate to severe congestive heart failure.

The objective of this multicenter, randomized, double-blind, placebo-controlled study was to determine the safety and efficacy of intravenous diltiazem in the treatment of 37 patients with rapid (ventricular rate, mean +/- SD 142 +/- 17 beats/min) atrial fibrillation or flutter and moderate to severe congestive heart failure (ejection fraction, mean +/- SD 36 +/- 14%; New York Heart Association class III [23 patients], class IV [14 patients]). During the double-blind portion of the study, patients received either intravenous diltiazem, 0.25 mg/kg over 2 minutes, or placebo followed 15 minutes later by diltiazem or placebo, 0.35 mg/kg over 2 minutes, if the first dose was tolerated but ineffective. Placebo nonresponders were given open-label intravenous diltiazem in a similar fashion as in the double-blind portion of the study. In the double-blind part of the study, 21 (18 with 0.25 mg/kg, 3 with an additional 0.35 mg/kg) of the 22 patients (95%) responded to diltiazem, and 0 of 15 patients (0%) responded to placebo (p < 0.001). All 15 patients (13 with 0.25 mg/kg and 2 with an additional 0.35 mg/kg) who received placebo during the double-blind period had a therapeutic response to diltiazem during open-label therapy. Overall, 36 of 37 patients (97%) had a therapeutic response to intravenous diltiazem. Heart rate response to diltiazem after the 2-minute bolus infusions consisted of a > or = 20% decrease in heart rate from baseline in 36 patients; in addition, 17 patients also had heart rates decreased to < 100 beats/min, whereas no patient had conversion to sinus rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

Simple step gradient elution of the major high-energy compounds and their catabolites in cardiac muscle using high-performance liquid chromatography.

The majority of high-energy nucleotides and their catabolites are separated in a single 13-min run using reversed-phase high-performance liquid chromatography. Economical step gradient elution of these compounds with a Nova Pak-A C18, 5-microns, 10 cm X 8 mm column accomplishes this separation with recoveries of 94-100% and sensitivities of 1-5 pmol. Furthermore, the total adenine nucleotide pool can now be quantitated precisely in a simple and easily automated procedure.

Adenine Nucleotides↗
PubMed1986

Protective metabolic effects of propranolol during total myocardial ischemia.

Clinical trials have shown an increase in survival in patients treated with beta blockers after infarction. In addition, the majority of patients undergoing myocardial revascularization are also treated preoperatively with beta blockers. It is commonly thought that beta blockers exert their protective effect primarily by decreasing heart rate and subsequent myocardial work. The present study was designed to determine whether beta blockade has any primary protective metabolic effects on globally ischemic myocardium. Thirty-four anesthetized dogs underwent total myocardial ischemia at 37 degrees C. High-energy nucleotide and lactate levels in left ventricular tissue samples were determined at control and at 15 minute intervals as well as at the onset of ischemic contracture in 24 dogs. Seventeen dogs were treated with propranolol before ischemia. The time to ischemic contracture in control dogs was 63.3 +/- 1.4 minutes compared with 75.9 +/- 2.2 minutes in the propranolol-treated group (p less than 0.01). In addition to significantly delaying the onset of ischemic contracture, propranolol also decreased the rate of anaerobic glycolysis during ischemia. Ischemic contracture occurred in the control group with an average adenosine triphosphate level of 1.26 +/- 0.08 mumol compared to 0.91 +/- 0.08 mumol/gm wet weight for the beta blocked group (p less than 0.0025). These are the first data suggesting that the protective effects of beta blockade may be related to a beneficial effect on ischemic myocardial metabolism allowing myocardium to survive with lower levels of adenosine triphosphate.

Adenine Nucleotides↗
PubMed1985

Central retinal artery occlusion during cardiac catheterization.

A massive embolus of the central retinal artery occurred during cardiac catheterization and selective coronary angiography. Anterior chamber paracentesis and coughing resulted in restoration of retinal blood flow and vision within two hours. In two other cases retinal arteriolar embolization was observed in patients who had minimal or no ocular symptoms after cardiac catheterization.

Aged↗