Russell M. Nelson

Electrophysiological Study of Human Heart Muscle

Membrane potential changes in human ventricular and atrial muscle, excised from patients undergoing open-heart surgery, were recorded by micro-electrodes in vitro. Mean ventricular resting and action potentials were −87 mv. and 115 mv., respectively. The mean atrial resting potential was −70 mv., mean action potential 75 mv. Two forms of atrial action potential were found, one having conventional contour, the other with prominent spike and plateau. A disturbance in repolarization is believed to underlie the latter type of atrial potential cycle. The relation between the upstroke velocity of the action potential and the extracellular sodium concentration and membrane potential was shown to be similar to that in other mammalian cardiac tissue. The mean conduction velocity determined in ventricular fibers (1.3 M./sec.) was somewhat greater than that of the dog, and the possible relationship to hypertrophy of the cardiac fibers in the preparations studied is described. The effect of increased rate and anoxia in reducing the action potential duration is like that found in the hearts of other mammals. The conductance type of inhibition was produced by acetylcholine in spontaneously beating atrial tissue. The excitatory effect of epinephrine was preceded by a transitory inhibition. The basic mechanisms underlying the action potential, automaticity and transmitter effects, derived from investigation of other mammalian cardiac tissue are applicable to the human heart.

The economic implications of infection in cardiac surgery.

To assess the economic impact of infection, the records of 496 patients aged 18 to 82 years (mean, 61 years) undergoing open-heart operations in 1981 and 1982 were reviewed, and the costs (length of stay, hospital charges, pharmacy charges) were compared for matched pairs of patients with and without infection who had coronary artery bypass grafting (CABG) procedures. Patients received a 5-day regimen of prophylactic cephalosporin. Operative site infections occurred within 6 months of operation in 17 patients (3.4%), urinary tract infections in 9 (1.8%), and pulmonary infections in 6 (1.2%). Early and late mortality was each 2%. No deaths were infection related, and no postoperative bacterial endocarditis occurred (minimum one-year follow-up). For the matched CABG patient in whom a postoperative wound infection developed, the average length of hospital stay was 16.7 days longer and the average hospital bill was

Attempted surgical division of the preexcitation pathway in the Wolff-Parkinson-White syndrome

8,118 greater, with the average cost to the hospital

Clinical and hemodynamic observations after surgical closure of large atrial septal defect complicated by heart failure

6,605 greater.

Coronary Bypass Surgery Early after Thrombolytic Therapy for Acute Myocardial Infarction

Abstract In a patient with type B Wolff-Parkinson-White syndrome, epicardial activation sequence mapping was carried out at the time of surgery for concurrent mitral stenosis. The patients preoperative course had been characterized by cardiac failure and repeated episodes of atrial tachyarrhythmia (fibrillation and flutter) which were difficult to control by conventional medical therapy. The mapping procedure revealed a broad area of preexcitation in the atrioventricular groove at the lateral right margin of the heart. Preexcitation was not present at the moment of incision, and attempted surgical interruption of the preexcitation pathway was unsuccessful. After surgery, there was a reduced incidence of tachyarrhythmia, but electrocardiographic evidence of preexcitation existed. Possible reasons for failure to sever the preexcitation pathway are considered.

Aortic Valve Replacement

Abstract Hemodynamic and clinical re-evaluation was carried out in 13 adults with a large atrial septal defect and preoperative evidence of left ventricular failure who underwent successful surgical closure of their lesion. The interval separating surgical correction and the postoperative study ranged from 5 months to 10 years (average 4.25 years). Subjective improvement, variable in extent, occurred in all patients, but a return to completely normal hemodynamics both at rest and during exercise occurred in only 1 patient. Eight patients had residual pulmonary hypertension at rest, and in 4 others this developed during exercise. Three patients had elevated pulmonary arterial wedge pressure at rest, and in 5 others it developed during exercise. Right atrial pressure was elevated in 2 at rest, and in 1 during exercise. Six of the 12 patients with postoperative flow data had an abnormally low resting cardiac index at rest, and 4 others had an inappropriately low flow response during exercise. There was no apparent correlation between the age at which the operation was performed and the degree of hemodynamic improvement. These data suggest that heart failure occurring in the patient with a large atrial septal defect does not preclude clinical improvement after surgical repair. There is, however, a high incidence of residual hemodynamic abnormalities.

Effective Use of Prophylactic Antibiotics in Open Heart Surgery

The safety of coronary bypass operations after coronary reperfusion with streptokinase for acute myocardial infarction is not well documented. Therefore we studied 23 consecutive patients (mean age, 59.5 years; 22 men) undergoing bypass operations a median of 5 days (range, 1 to 23 days) after thrombolysis (streptokinase). The control group consisted of 169 concurrent patients of similar mean age (58.8 years) having bypass operations for standard indications. The preoperative angiographic ejection fraction was 68 +/- 14% in the control patients and 61 +/- 14% in the streptokinase group (p less than 0.05). The number of diseased vessels (70% stenosis or greater) averaged 2.6 in control and 2.3 in streptokinase patients. A previous myocardial infarction had occurred in 42% of the controls and all of the streptokinase patients. Aortic cross-clamp times did not differ between the two groups (80 +/- 35 minutes for the controls and 68 +/- 25 minutes for the streptokinase group). Cardiopulmonary bypass times were similar: 108 +/- 45 minutes in the controls versus 109 +/- 28 minutes in the streptokinase group. Grafts per patient averaged 3.7 +/- 1.5 for the controls versus 2.8 +/- 1.1 for the streptokinase patients (p less than 0.01). Difficult operative hemostasis was noted in 4% of both groups. Inotropic support was given postoperatively to 11% of the control and 13% of the streptokinase patients (p = not significant). Measured blood loss during the first 48 hours postoperatively was similar, averaging 809 ml in controls and 776 ml in the streptokinase group. Blood product replacement was also comparable: mean, 713 ml in the control group versus 759 ml in the streptokinase group.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of harvesting technique on endothelial preservation in saphenous veins

he development of the ball-valve prosthesis for replacement of the diseased aortic valve by Starr et al. [22] extended operability T to many patients for whom palliative surgical treatment had not been previously available. Many of these patients now survive and are subject to the benefits and risks of this prosthesis, for which the long-term results are as yet incompletely assessed. Moreover, with the recent development of significant alterations in the design of prosthetic valves and the interest in the use of allografts and xenografts to replace the aortic valve, it seemed desirable to evaluate our results to date with the use of the Starr-Edwards aortic valve prosthesis.