Michael A. Savitt

Active compression-decompression resuscitation: Effect on resuscitation success after in-hospital cardiac arrest

Objectives. The purpose of this study was to test the hypothesis that active compression-decompression would improve resuscitation success in human subjects after cardiac arrest. Background. Active compression-decompression cardiopulmonary resuscitation is a new method that improves cardiopulmonary hemodynamic function in animal models and humans after cardiac arrest. Methods. We conducted a prospective randomized clinical trial in patients with in-hospital cardiac arrest. Patients were assigned to receive standard manual or active compression-decompression cardiopulmonary resuscitation. The primary study end points were spontaneous return of circulation, 24-h survival and survival to hospital discharge. Results. Fifty-three consecutive patients after cardiac arrest undergoing 64 resuscitation attempts were studied (30 women, 23 men; mean [± SD] age 71 ± 13 years, range 38 to 96). Spontaneous return of circulation was observed in 24 (47%) of 53 patients and was increased in patients receiving active compression-decompression compared with those receiving standard manual cardiopulmonary resuscitation (15 [60%] of 25 vs. 9 [32%] of 28, respectively, p = 0.042); 24-h survival was increased (12 [48%] of 25 vs. 6 [21%] of 28, respectively, p = 0.041); and there was a trend toward improved survival to hospital discharge (6 [24%]of 25 vs. 3 [11%]of 28, respectively, p = 0.198) when active compression-decompression was compared with standard manual cardiopulmonary resuscitation. Conclusions. Active compression-decompression cardiopulmonary resuscitation improves return of spontaneous circulation and 24-h survival after in-hospital cardiac arrest. Active compression-decompression cardiopulmonary resuscitation appears to be a beneficial adjunct to standard manual cardiopulmonary resuscitation.

Active compression-decompression resuscitation: effects on pulmonary ventilation

This investigation was designed to test the hypothesis that active compression-decompression resuscitation is able to independently provide improved levels of minute ventilation when compared to high-impulse manual cardiopulmonary resuscitation (CPR). Eight adult beagles (10-15 kg) were studied after induction of ventricular fibrillation. Single 1-min CPR trials were performed while arterial blood gases and minute ventilation were monitored. ACD and high-impulse CPR were performed sequentially, in random order at compression rates of 120/min, 1.5- to 2.0-inch compression depth and 50% duty cycle. Minute ventilation averaged 3.6 +/- 0.77 1 during high-impulse CPR and increased to 4.9 +/- 0.88 1 during ACD CPR. No difference was observed in arterial blood pH, PCO2, or PO2 when ACD was compared to high-impulse CPR. We conclude that ACD CPR provides improved levels of minute ventilation when compared to high-impulse manual CPR in this canine model of cardiac arrest. Improved minute ventilation may contribute to the mechanism of improved cardiopulmonary hemodynamics reported in previous investigations of ACD CPR. Further investigation is warranted to determine the effects of ACD CPR on pulmonary ventilation in human subjects after cardiac arrest.

The biphasic mechanism of blood flow during cardiopulmonary resuscitation: A physiologic comparison of active compression-decompression and high-impulse manual external cardiac massage

STUDY OBJECTIVE Dismal survival in patients receiving standard manual CPR provided the rationale for the investigation of alternate methods of closed-chest circulatory support. Active compression-decompression (ACD) and high-impulse CPR are alternatives to standard manual CPR. This study was designed to test the hypothesis that ACD CPR provides superior cardiopulmonary hemodynamics due to an active decompression phase when compared with high-impulse manual CPR. PARTICIPANTS Hemodynamics were studied during ACD and high-impulse CPR in eight adult beagles. DESIGN Four animals were chronically instrumented and four were studied acutely. In an additional four animals, ACD was compared with sham ACD CPR. Each CPR technique was performed sequentially for 2 minutes, in random order, at a rate of 120, 50% duty cycle, and 1.5 to 2.0 in of compression depth. Measurements obtained included aortic, right atrial, left ventricular, and coronary perfusion pressures (in mm Hg); pulmonary artery flow, and left ventricular dimension. RESULTS ACD maximized cardiopulmonary hemodynamics, including coronary perfusion pressure and stroke volume, compared with both high-impulse manual and sham ACD CPR. ACD CPR also increased left ventricular pressure change per unit time during decompression, and these changes correlated well with left ventricular volume changes. CONCLUSION In the intact dog, ACD CPR generates physiologically and statistically superior hemodynamics when compared with high-impulse manual CPR. Improved blood flow seems to be related to more efficient ventricular filling and emptying. These findings emphasize the biphasic nature of CPR and the importance of active decompression.

A simple technique for aortic valve replacement in patients with a patent left internal mammary artery bypass graft

Aortic valve replacement in patients with a patent left internal mammary artery graft is often a challenge because of the difficulties with dissection of the left internal mammary artery and optimum myocardial protection. We describe a simple technique of aortic valve replacement with a beating heart and continuous coronary perfusion for this difficult group of patients.

Off-pump coronary artery bypass grafting decreases morbidity and mortality in a selected group of high-risk patients

BACKGROUND The ideal indication for off-pump coronary artery bypass grafting (OPCABG) has yet to be defined. High-risk surgical patients may benefit the most when cardiopulmonary bypass (CPB), aortic cross clamping, and cardioplegic arrest are avoided. The aim of this study was to determine whether off-pump coronary artery bypass grafting might decrease the operative morbidity and mortality in a select group of high-risk patients with multivessel coronary artery disease. METHODS Utilizing a Parsonnet risk stratification model we analyzed prospectively collected data on a cohort of high-risk coronary artery disease patients, which were operated on with beating-heart technology by the same group of surgeons in a tertiary care university medical center. High-risk patients were defined as those with a Parsonnet score of 15 or greater. RESULTS Fifty-seven multivessel disease OPCABG patients (over a period of 2 years) had markedly increased Parsonnet scores (24.3 +/- 10.6). The average ejection fraction of the patients was 42% (+/-12.3) and their age ranged from 52 to 85 years (mean 70.6 +/- 10.4, 26% women). Unstable angina was present in 42 patients (74%) and 10 patients underwent OPCABG within 24 hours of the occurrence of acute myocardial infarction. In addition to severe coronary artery disease 32% of the patients presented with congestive heart failure, insulin-dependent diabetes (18%), renal failure (22%), peripheral vascular disease (31%), pulmonary disease (18%), and neurologic disorders (14%). An average of 2.6 +/- 0.9 grafts/patient were performed and the posterior descending artery or marginal branches of the circumflex artery or both were grafted in 90%. The 30-day mortality rate was 3.5% (n = 2). CONCLUSIONS OPCABG can be performed with a reasonable low morbidity and mortality in this select group of high-risk patients. OPCABG is a reasonable, and might even be preferable, operative strategy in this high-risk group of patients.

Mechanical determinants of myocardial oxygen consumption in conscious dogs

A new practical descriptor of metabolic to mechanical myocardial energy transfer (MET), termed the virtual work model, was evaluated in 32 conscious dogs and in 8 isolated canine hearts. An index of total mechanical energy expenditure (TME) was calculated as the sum of external energy (stroke work) and an internal energy index of heat (left ventricular end-diastolic volume times left ventricular mean ejection pressure). Physiological comparison of TME (x-axis) and myocardial oxygen consumption (MVO2; y-axis) yielded highly linear MET relationships (mean r = 0.93 +/- 0.07), with an average slope of 0.86 +/- 0.39 (SD) and a y-intercept of 9.1 +/- 6.4 mW/ml myocardium. The linear MVO2-TME relationship did not vary under steady-state vs. dynamic vena caval occlusion, increased heart rate, increased afterload, or increased inotropic state with calcium infusion. Compared with five other indexes of myocardial energetics, the virtual work model of MET was the most linear, the most practical in not requiring determination of the end-systolic pressure-volume relationship, and the most accurate predictor of MVO2 under normal and altered hemodynamic conditions.

Left ventricular adaptation to aortic regurgitation in conscious dogs

OBJECTIVE Cardiac failure as a result of valvular heart disease remains a major clinical problem that frequently leads to ventricular dysfunction, myocardial failure, and even death. The development of irreversible myocardial damage may be especially insidious in volume overload as a result of aortic or mitral regurgitation. METHODS AND RESULTS Left ventricular wall volume, ventricular function, and myocardial performance were assessed in 10 chronically instrumented conscious dogs before and after creation of aortic regurgitation. Left ventricular wall volume was measured by serial echocardiography. Left ventricular function was assessed by total cardiac output, stroke work, the slope of the Frank-Starling relationship, and the slope of the end-systolic pressure-volume relationship. Myocardial performance was assessed by the slope of the myocardial power output versus end-diastolic strain relationship. End-diastolic wall stress and volume both increased acutely and remained elevated after creation of aortic regurgitation. Peak systolic wall stress increased initially (1 to 3 weeks) from 336 +/- 30 to 369 +/- 55 mm Hg but returned to control values as left ventricular wall volume increased from 78 +/- 13 to 88 +/- 16 ml after development of compensatory hypertrophy. Left ventricular systolic function remained constant or increased and was maintained initially by increased myocardial performance, which returned to baseline levels after the development of compensatory hypertrophy. CONCLUSIONS Myocardial performance and ventricular function vary independently in aortic regurgitation. Measures of myocardial performance such as the myocardial power output versus end-diastolic strain relationship may be useful in clinical assessment of aortic regurgitation.

Use of Bachmann's bundle for bipolar atrial pacing.

In patients with acute or chronic right coronary ischemia, pacing with temporary right atrial epicardial wires is sometimes difficult due to high electrical thresholds. A simple and reproducible technique is described to assure atrial capture and appropriate atrial pacing under these conditions.

Mitral Valve Repair on the Beating Perfused Heart

It is difficult to assess the success of mitral valve repair in the arrested heart. Various techniques have been described. Transesophageal echocardiogram (TEE) provides excellent two-dimensional evaluation of the repair, but three-dimensional anatomic characteristics are limited. We describe a simple technique for performing mitral valve repair on the beating heart. This allows accurate evaluation of valvular competence and three-dimensional anatomic characteristics prior to closure of the atriotomy.

Active compression decompression resuscitation: Effect on resuscitation success after in-hospital cardiac arrest

OBJECTIVES The purpose of this study was to test the hypothesis that active compression-decompression would improve resuscitation success in human subjects after cardiac arrest. BACKGROUND Active compression-decompression cardiopulmonary resuscitation is a new method that improves cardiopulmonary hemodynamic function in animal models and humans after cardiac arrest. METHODS We conducted a prospective randomized clinical trial in patients with in-hospital cardiac arrest. Patients were assigned to receive standard manual or active compression-decompression cardiopulmonary resuscitation. The primary study end points were spontaneous return of circulation, 24-h survival and survival to hospital discharge. RESULTS Fifty-three consecutive patients after cardiac arrest undergoing 64 resuscitation attempts were studied (30 women, 23 men; mean [+/- SD] age 71 +/- 13 years, range 38 to 96). Spontaneous return of circulation was observed in 24 (47%) of 53 patients and was increased in patients receiving active compression-decompression compared with those receiving standard manual cardiopulmonary resuscitation (15 [60%] of 25 vs. 9 [32%] of 28, respectively, p = 0.042); 24-h survival was increased (12 [48%] of 25 vs. 6 [21%] of 28, respectively, p = 0.041); and there was a trend toward improved survival to hospital discharge (6 [24%] of 25 vs. 3 [11%] of 28, respectively, p = 0.198) when active compression-decompression was compared with standard manual cardiopulmonary resuscitation. CONCLUSIONS Active compression-decompression cardiopulmonary resuscitation improves return of spontaneous circulation and 24-h survival after in-hospital cardiac arrest. Active compression-decompression cardiopulmonary resuscitation appears to be a beneficial adjunct to standard manual cardiopulmonary resuscitation.