Joseph A. Gascho

Prognostic utility of the exercise thallium-201 test in ambulatory patients with chest pain: comparison with cardiac catheterization.

The goal of this study was to determine the prognostic utility of the exercise thallium-201 stress test in ambulatory patients with chest pain who were also referred for cardiac catheterization. Accordingly, 4 to 8 year (mean +/- 1SD, 4.6 +/- 2.6 years) follow-up data were obtained for all but one of 383 patients who underwent both exercise thallium-201 stress testing and cardiac catheterization from 1978 to 1981. Eighty-three patients had a revascularization procedure performed within 3 months of testing and were excluded from analysis. Of the remaining 299 patients, 210 had no events and 89 had events (41 deaths, nine nonfatal myocardial infarctions, and 39 revascularization procedures greater than or equal to 3 months after testing). When all clinical, exercise, thallium-201, and catheterization variables were analyzed by Cox regression analysis, the number of diseased vessels (when defined as greater than or equal to 50% luminal diameter narrowing) was the single most important predictor of future cardiac events (chi 2 = 38.1) followed by the number of segments demonstrating redistribution on delayed thallium-201 images (chi 2 = 16.3), except in the case of nonfatal myocardial infarction, for which redistribution was the most important predictor of future events. When coronary artery disease was defined as 70% or greater luminal diameter narrowing, the number of diseased vessels significantly (p less than .01) lost its power to predict events (chi 2 = 14.5). Other variables found to independently predict future events included change in heart rate from rest to exercise (chi 2 = 13.0), ST segment depression on exercise (chi 2 = 13.0), occurrence of ventricular arrhythmias on exercise (chi 2 = 5.9), and beta-blocker therapy (chi 2 = 4.3). The exclusion of myocardial revascularization procedures as an event did not change the results significantly. Although the number of diseased vessels was the single most important determinant of future events, the exercise thallium-201 stress test when considered as a whole (which included the number of segments demonstrating redistribution on delayed thallium-201 images, change in heart rate from rest to exercise, ST segment depression on the electrocardiogram, and ventricular premature beats on exercise) was equally powerful (chi 2 = 41.6). Combination of both catheterization and exercise thallium-201 data was superior to either alone (chi 2 = 57.5) for determining future events. Exercise stress test alone (without thallium-201 data) was inferior to the exercise thallium-201 stress test or cardiac catheterization for predicting future events (chi 2 = 30.6).(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of cardiac hypertrophy secondary to hypertension on the coronary circulation

For many years clinicians have suspected that hypertrophied ventricles have an inadequate coronary circulation. Recent studies have confirmed early observations that flow per gram in hypertrophied ventricles is normal at rest. However, coronary vascular resistance is greatly increased when hypertension is the cause of left ventricular hypertrophy. Studies that have employed labeled microspheres to assess regional myocardial perfusion have shown that the transmural distribution of myocardial perfusion is often abnormal in dogs with left ventricular hypertrophy. In addition, studies of cardiac hypertrophy in many animal models have shown that maximal coronary vasodilatation is limited substantially. Furthermore, when hypertrophied hearts are subjected to a physiologic stress that induces coronary vasodilatation, endocardial underperfusion occurs frequently. Thus, studies in animals suggest that cardiac hypertrophy adversely affects the coronary circulation. The availability of new techniques for estimating phasic and transmural coronary blood flow in man should make it possible to extend these studies to patients with cardiac hypertrophy.

Reduction of prehospital, ambulance and community coronary death rates by the community-wide emergency cardiac care system

Initiation of quick prehospital cardiopulmonary resuscitation and emergency cardiac care completed the total system needed to provide emergency and convalescent coronary care for a community. Subsequently, annual community rates for coronary death during ambulance transport fell by 62 per cent and for prehospital coronary death by 26 per cent in people under 70 years of age. In cardiac arrest due to acute myocardial infarction, prompt successful prehospital correction of ventricular fibrillation and asystole yielded long-term survival in two thirds of cases. This 66 per cent success rate of prehospital cardiopulmonary resuscitation and emergency cardiac care is identical to contemporary international experience. Precordial thump-version with the fist and precordial fist pacing appeared logical additions to prehospital cardiopulmonary resuscitation and emergency cardiac care technics. Community lives saved yearly were 15.2/100,000 people aged 30 to 69 years and 6.4/100,000 total population. Simultaneously, annual community rates for coronary death as a cause of death and coronary death per 1,000 people fell significantly by 15 and 17 per cent, respectively. Unquantifiable influences included prehospital relief of ischemic chest pain; prehospital correction of acute dysautonomia; prehospital abolition of otherwise prefatal dysrhythmias; similar treatment for acute myocardial infarction in the emergency department, in the inhospital mobile coronary care unit and in the progressive intermediate coronary convalescent unit; and general community education through the media of newspapers, radio and television. The present frequency of coronary death during ambulance transport, 9 to 22 per cent of prehospital coronary deaths in this and other surveys, suggests that the prehospital cardiopulmonary resuscitation and emergency cardiac care component needs improvement in many communities. By reducing prehospital and ambulance coronary death rates, prehospital cardiopulmonary resuscitation and emergency cardiac care for acute myocardial infarction constitutes an essential component of the total system approach to emergency coronary care. Since prehospital cardiopulmonary resuscitation and emergency cardiac care have cheaply and effectively expedited and abbreviated hospitalization for acute myocardial infarction, and lowered community death rates from coronary artery disease, its adoption throughout the United States and the western world seems justified.

Prevalence of high-risk thallium-201 scintigraphic findings in left main coronary artery stenosis: Comparison with patients with multiple- and single-vessel coronary artery disease

To determine the prevalence of high-risk thallium-201 (Tl-201) scintigraphic findings in patients with left main (LM) coronary artery disease (CAD), quantitative exercise Tl-201 scintigrams were analyzed in 295 consecutive patients with angiographic (greater than or equal to 50% stenosis) CAD, of which 43 (14%) had greater than or equal to 50% LM stenosis. A high-risk scintigram was defined as one that demonstrated (1) a LMCAD scintigraphic pattern (greater than or equal to 25% homogeneous decrease in Tl-201 activity in the middle and upper septal and posterolateral walls on the 45 degree left anterior oblique projection); (2) abnormal Tl-201 uptake or washout in multiple vascular scan segments indicative of multivessel disease; and (3) increased lung Tl-201 uptake on the initial anterior projection image. Of the 43 patients with LMCAD, 41 (95%) had an abnormal scintigram. Thirty-three (77%) had 1 or more high-risk scintigraphic findings, including 29 (67%) with a multivessel CAD scan pattern, of which 6 (14%) demonstrated a typical LMCAD pattern; and 18 (42%) with abnormal lung Tl-201 uptake. The prevalence of a high-risk scintigram in patients with LMCAD was significantly greater than that in 53 patients with 3-vessel disease (58%) (p = 0.05), 99 patients with 2-vessel disease (60%) (p = 0.04) and 100 patients with 1-vessel disease (41%) (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of direct-current countershocks on regional myocardial contractility and perfusion. Experimental studies.

Very high energy electrical countershocks can cause morphologic damage to the myocardium. In this study we searched for functional correlates of these shock-induced morphologic changes. We used ultrasonic sonomicrometers to measure myocardial contractility and radiolabeled microspheres to assess perfusion. Acute and chronic experiments were conducted in 45 dogs, assessing the effect of both direct (epicardial) and transthoracic shocks on beating and fibrillating hearts. High-energy or rapidly repeated epicardial shocks caused subepicardial contraction abnormalities. This indicates that electrical current delivered to the myocardium in sufficiently high amounts and concentration can cause functional damage. Thus, in open-chest defibrillation during cardiac surgery, low energies (10–20 J) should be used initially and higher energies resorted to only if lower-energy shocks fail. However, single and multiple transthoracic shocks up to 460 J delivered energy caused no detectable contraction abnormalities. Myocardial perfusion did not fall after shocks. Thus, high-energy transthoracic shocks may have no deleterious effects on the contraction and perfusion of normal myocardium.

Determinants of defibrillation: Prospective analysis of 183 patients

Previous studies have suggested that a number of factors may influence the ability to defibrillate: the transthoracic resistance and resultant current flow, the paddle electrode size, the duration of preshock ventricular fibrillation (VF) and cardiopulmonary resuscitation, metabolic abnormalities, body weight, the shock energy selected, and whether the patient is receiving lidocaine. To examine the effect of these variables, a prospective study was conducted of 183 patients who received direct-current shocks for VF. Overall defibrillation rates approached 90%, even in patients with secondary VF, but rates of successful resuscitation and survival were much lower. Patients who never defibrillated despite multiple shocks had a prolonged duration of cardiopulmonary resuscitation preceding the first shock (21 +/- 14 minutes) and systemic hypoxia and acidosis. These conditions tended to occur in patients who initially had cardiac arrest from causes other than VF: asystole, severe bradycardia and electromechanical dissociation. In such patients, VF developed only as a late event, which was then often unresponsive to attempted defibrillation. The other factors examined were not major determinants of defibrillation.

Determinants of ventricular defibrillation in adults.

Conventional defibrillators which stored no more than 400 J and used damped sine wave pulses defibrillated 240 of 253 (95%) episodes of ventricular fibrillation (VF) in 94 prospectively assessed resuscitations in 88 adults. Shocks of 80-240 J (under 3 J/kg) delivered to the chest wall defibrillated more often than higher energy levels. Defibrillation rate did not correlate with weight. Defibrillation was determined by the diagnosis and setting in which VF occurred. Patients with acute myocardial infarction (AMI) and primary VF or with coronary disease and no AMI defibrillated more easily than patients with AMI and secondary VF or with no coronary disease. VF in a terminal patient (agonal VF) defibrillated less often than VF in other clinical situations. Age, weight, delivered energy, duration of pulse wave, and duration of VF had little, if any, influence on rate of defibrillation. These data fail to support the use of more expensive, high-output defibrillators sold by 11 of 14 American manufacturers.

Cardiac catheterization in morbidly obese patients

The safety and findings of cardiac catheterization and coronary angiography in morbidly obese patients with suspected coronary heart disease (CHD) have not been fully examined in the modern era. From a database of 4,978 patients undergoing diagnostic cardiac catheterization, we identified 110 with morbid obesity (body mass ≥ 145 kg and body mass index ≥ 40 kg/m2). Relative to all the other patients in this database, morbidly obese patients had a lower prevalence of CHD (45% vs. 72%; P < 0.05), reflecting a higher prevalence of false positive noninvasive tests. Overall, noninvasive tests were only 75% sensitive and 39% specific for CHD in this group. Use of radial access (66%) and femoral closure devices (24%) was much more frequent in the morbidly obese cohort. Complications were no more frequent in the morbidly obese group, with major (0 vs. 0.9%) and minor (4.7% vs. 3.5%) adverse outcomes being similar to the rest of the database. We conclude that cardiac catheterization using the radial artery or a femoral closure device is a safe and effective method of evaluating CHD in morbidly obese patients. In contrast, noninvasive testing is frequently not definitive and may be misleading. Cathet Cardiovasc Intervent 2002;56:174–177.

Myocardial thallium-201 kinetics during coronary occlusion and reperfusion: influence of method of reflow and timing of thallium-201 administration

Thallium-201 (201Tl) uptake and redistribution kinetics were examined in an open-chest canine preparation of occlusion and reperfusion. Seven dogs (group I) underwent 3 hr of sustained occlusion and received 1.5 mCi of 201Tl after 40 min of occlusion of the left anterior descending coronary artery (LAD). Group II (n = 18) underwent 60 min of LAD occlusion followed by sudden and total release of the ligature. Group IIa (n = 8) received intravenous 201Tl during occlusion of the LAD, whereas group IIb (n = 10) received intravenous 201Tl at the time of peak reflow. Group III dogs (n = 26) also underwent 60 min of LAD occlusion that was followed by gradual reflow through a residual critical stenosis. Animals in this group also received 201Tl either before (IIIa; n = 16) or after reflow was established (IIIb; n = 10). In group I, the relative 201Tl gradient (nonischemic minus ischemic activity) decreased from 88 +/- 8% (mean +/- SEM) to 59 +/- 6% during 3 hr of coronary occlusion (p = .034). After rapid and total reperfusion (group IIa), this gradient decreased from 71 +/- 6% during occlusion to 26 +/- 5% after reflow (p less than .001). After slow reperfusion through a residual stenosis (group IIIa), the gradient decreased from 81 +/- 5% to 31 +/- 5% (p less than .001) (p = .56 compared with group IIa). In rapidly reperfused dogs receiving intravenous thallium during peak reflow (IIb), initial 201Tl activity in the ischemic zone was 155 +/- 20% of initial normal activity and fell to 93 +/- 13% of normal after 2 hr of reperfusion. Similarly, in dogs reperfused slowly through a critical stenosis (IIIb), which received 201Tl during reflow, 201Tl activity soon after reflow was 94 +/- 4% of initial normal and decreased to 80 +/- 6% at 2 hr of reperfusion (p = .10). Histochemical evidence of necrosis was present in the biopsy region in 80% of the 20 dogs subjected to triphenyl tetrazolium chloride (TTC) staining. Microsphere-determined transmural blood flow was similar in all groups during LAD occlusion and final flows after 2 hr were comparable in all subgroups undergoing reflow. Ischemic zone flow (% normal) was significantly higher at the time of 201Tl administration in groups IIb (192 +/- 25%) and IIIb (110 +/- 5%), which received 201Tl during reflow, than in groups IIa (31 +/- 9%) and IIIa (22 +/- 5%), which received 201Tl during occlusion.(ABSTRACT TRUNCATED AT 400 WORDS)

Hemodynamic Effects of Volume Expansion and Nitroprusside Compared with Pericardiocentesis in Patients with Acute Cardiac Tamponade

Acute cardiac tamponade is a medical emergency that requires urgent therapy. Removal of pericardial fluid by pericardiocentesis or by open surgical drainage is effective,1 2 3 but delays may occur ...