Robert A. Silverberg

Clinical and experimental studies on electromechanical dissociation.

Electromechanical dissociation (EMD) is the most frequent cause of unsuccessful cardiac resuscitation in critically ill patients. In a clinical study of cardiac arrest, including 54 episodes in 50 fully monitored patients, 14 episodes of ventricular fibrillation were observed and seven were reversed. In the remaining 40 instances, 36 cases of EMD were initially observed. Four patients had asystole. None of the patients with EMD or asystole were successfully resuscitated.For objective study of EMD and its treatment, we developed an experimental model in which ventricular fibrillation was induced in mechanically ventilated dogs. EMD was predictably observed when, after an interval of 120 seconds, ventricular fibrillation was reversed with an external countershock. Neither metabolic acidosis nor metabolic alkalosis modified the incidence of EMD. A few dogs were pretreated with glucose-insulin- potassium or pharmacologic doses of methylprednisolone, but this did not clearly reduce the incidence of EMD. However, the onset of EMD was delayed when the body temperature of the animal was spontaneously reduced.

Noninvasive diagnosis of coronary artery disease: the cardiokymographic stress test.

Stress–induced abnormalities of regional left ventricular wall motion were assessed by cardiokymography (CKG) during the course of maximal treadmill exercise tests in 157 patients, of whom 122 subsequently underwent coronary angiography. Seventy patients had significant angiographic coronary artery disease and 52 were normal. Forty–one of the 70 patients developed >0.1 mV ST–segment depression (ECG sensitivity 59%) and 52 of 70 patients developed abnormal systolic outward motion by CKG (CKG sensitivity 74%). Among the 52 normals, 36 had negative ECG stress tests (ECG specificity 69%) and 49 had normally sustained systolic inward motion by CKG (CKG specificity 94%). The stress CKG was normal in 15 of the 16 false–positive stress ECGs; the stress ECG was correctly normal in two of the three false–positive stress CKG tests. Only one normal patient had concordantly false–positive ECG and CKG tests. The predictive accuracy of concordant ECG and CKG interpretations was, therefore, higher than either test alone.These data suggest that regional wall motion abnormalities, which are sensitive and specific markers of myocardial ischemia, may be detected noninvasively by CKG. We concluded that CKG helps identify falsepositive and false–negative ECG stress tests and improves the diagnostic accuracy of stress testing for detection of coronary artery disease.

Midterm Benefits of Preoperative Statin Therapy in Patients Undergoing Isolated Valve Surgery

BACKGROUND Recent data have suggested that statins are associated with reduced early mortality and cardiovascular events after valvular heart surgery. The midterm effects of preoperative statin therapy in the setting of valvular heart surgery are presently unclear. METHODS All patients (n=2,120) who underwent a valvular procedure between April 2004 and April 2010 were identified. Patients undergoing concomitant coronary artery bypass graft surgery were excluded. Two patient groups were studied: those who received preoperative statin therapy (n=663; 31.3%) and those who did not (n=1,457; 68.7%). Propensity score matching resulted in 381 matched pairs, thus addressing baseline risk imbalances. Thirty-day mortality, readmission rates, postoperative complications, and length of stay were analyzed. Late survival was ascertained by the Social Security Death Index. RESULTS In the matched group, 30-day mortality was 1.3% (5 of 381) for statin-treated patients versus 4.2% (16 of 381) for statin-untreated patients (p=0.03). After a mean follow-up of 33±23 months, statin therapy was associated with significantly reduced mortality (hazard ratio 0.63, 95% confidence interval: 0.43 to 0.93, p=0.019), independent of known cardiac risk factors. Weighted log rank tests revealed that the mortality difference between the two cohorts occurred early after surgery (p=0.015). Statin users were less likely to be readmitted to the intensive care unit (3.4% versus 8.1%, p=0.01). There were no other significant differences between the two groups in terms of postoperative complications and length of stay. CONCLUSIONS Preoperative statin administration is associated with early reductions in mortality among patients undergoing isolated valvular heart surgery, leading to improved late survival. Future prospective analyses are warranted to optimize statin therapy in this patient population.

Assessment of the functional significance of coronary artery disease with atrial pacing and cardiokymography

Abstract Thirty-six patients were studied during the course of cardiac catheterization to assess the role of cardiokymography and atrial pacing in the functional evaluation of angiographic coronary arterial stenosis. Only 4 of 25 patients with greater than 50 percent diameter stenosis of at least one major vessel had 0.1 mv or greater S-T segment depression at a paced heart rate of 123 ± 25/min, and 2 of 11 normal patients revealed a similar response (P = not significant). In contrast, in 22 of 25 patients systolic outward motion developed as determined with cardiokymography during the same pacing period, whereas in only 1 of 11 normal patients a similar abnormality did develop (P These data are consistent with the view that regional wall motion abnormalities are highly sensitive and specific markers of ischemia and that such abnormalities may be detected noninvasively with cardiokymography. It is concluded that atrial pacing in conjunction with cardiokymography is applicable to the functional assessment of ischemic heart disease and may provide a means for objective evaluation of the significance of angiographically observed coronary stenosis.

Time-resolved three-dimensional phase contrast MRI evaluation of bicuspid aortic valve and coarctation of the aorta

A 41-year-old man with a bicuspid aortic valve (BAV) and coarctation of the aorta, as visualized by 2D phase contrast cardiovascular magnetic resonance imaging (CMR) ( Figure 1D , Supplementary data online, Videos S1 ) and contrast enhanced MR angiography ( Figure 1A ), was referred for evaluation by time-resolved 3D phase contrast (4D flow) CMR to assess the flow velocity through the coarctation and provide aortic flow characterization. Findings of the comprehensive examination demonstrate the complex haemodynamic patterns that emerge throughout the aorta secondary …

Cardiokymographic wall motion pattern in patients with acute myocardial infarction

We studied 50 patients with acute myocardial infarction by cardiokymography to record anterior left ventricular wall motion. Systolic outward motion was observed in 46 of 50 patients (92%). Holosystolic outward motion was characteristic of acute anterior infarction (93%) and acute subendocardial infarction (89%) but was less common in acute inferior infarction (29%). Partial systolic outward motion was seen in 8 of the 14 patients with acute inferior infarction, but only in 2 of 36 patients with acute anterior and subendocardial infarction. Cardiokymographic abnormalities were seen in more precordial locations in acute anterior (80%) and subendocardial infarction (97%) than in inferior infarction (74%). Holosystolic outward motion was seen in 75% of all locations in acute anterior and subendocardial infarction and only in 23% in acute inferior infarction. Thus both the extent and the severity of abnormal systolic outward motion clearly separated inferior infarction from anterior and subendocardial infarction. Dynamic changes in wall motion contraction patterns were observed during the course of acute myocardial infarction; both improvement and deterioration were observed. Cardiokymography is a simple, non-invasive method to assess changes in left ventricular segmental wall motion in patients with acute myocardial infarction.

MIDTERM BENEFITS OF PERIOPERATIVE STATIN THERAPY IN PATIENTS UNDERGOING ISOLATED VALVULAR HEART SURGERY: FIVE-YEAR SURGICAL EXPERIENCE

Methods: All patients (n=1855) who underwent a valvular procedure between April 2004 and April 2009 were identified retrospectively. Patients (n=644) undergoing concomitant coronary surgery were excluded. Of the remaining 1211 patients, 361 (29.8%) were administered statins before and after surgery (group 1) and 850 (70.2%) were not (group 2). Late survival was ascertained by the Social Security Death Index and cause of death was verified by database review. Adjusted hazard ratios (aHR), adjusted odds ratios (aOR) and multiple regression coefficients accounted for patient demographics, known preoperative risk factors, surgical characteristics and concomitant medications.

Segmental Myocardial Wall Motion and Myocardial Ischemia

Segmental wall motion abnormalities reliably occur with acute ischemia and can be detected during angina pectoris, with myocardial infarction, and during stress in patients with significant coronary artery disease. Some chronic contraction abnormalities can be reversed by successful revascularization surgery[1], as well as by physiological interventions that reduce ischemia by improving the myocardial oxygen sypply-demand ratio[2–5]. Demonstration of reversible asynergy during intervention ventriculography can aid in selecting low-risk patients who will benefit from aortocoronary bypass surgery, whereas irreversible asynergy signifies infarction and is associated with a poorer prognosis after surgery[2]. Furthermore, the extent and location of segmental contraction abnormalities determines the level of global ventricular pump function which is a major determinant of morbidity and mortality after myocardial infarction[6,7]. The chapter will describe the effects of acute ischemia upon the mechanical behavior of myocardial segments, and will review the use of cardiokymography to detect and record cardiac motion in man.