Effectiveness and limitations of beta-blocker therapy in congenital long-QT syndrome.

BACKGROUND: beta-blockers are routinely prescribed in congenital long-QT syndrome (LQTS), but the effectiveness and limitations of beta-blockers in this disorder have not been evaluated. METHODS AND RESULTS: The study population comprised 869 LQTS patients treated with beta-blockers. Effectiveness of beta-blockers was analyzed during matched periods before and after starting beta-blocker therapy, and by survivorship methods to determine factors associated with cardiac events while on prescribed beta-blockers. After initiation of beta-blockers, there was a significant (P<0.001) reduction in the rate of cardiac events in probands (0.97+/-1.42 to 0.31+/-0.86 events per year) and in affected family members (0. 26+/-0.84 to 0.15+/-0.69 events per year) during 5-year matched periods. On-therapy survivorship analyses revealed that patients with cardiac symptoms before beta-blockers (n=598) had a hazard ratio of 5.8 (95% CI, 3.7 to 9.1) for recurrent cardiac events (syncope, aborted cardiac arrest, or death) during beta-blocker therapy compared with asymptomatic patients; 32% of these symptomatic patients will have another cardiac event within 5 years while on prescribed beta-blockers. Patients with a history of aborted cardiac arrest before starting beta-blockers (n=113) had a hazard ratio of 12.9 (95% CI, 4.7 to 35.5) for aborted cardiac arrest or death while on prescribed beta-blockers compared with asymptomatic patients; 14% of these patients will have another arrest (aborted or fatal) within 5 years on beta-blockers. CONCLUSIONS: beta-blockers are associated with a significant reduction in cardiac events in LQTS patients. However, syncope, aborted cardiac arrest, and LQTS-related death continue to occur while patients are on prescribed beta-blockers, particularly in those who were symptomatic before starting this therapy.

Acute myocardial infarction associated with single vessel coronary artery disease: an analysis of clinical outcome and the prognostic importance of vessel patency and residual ischemic myocardium.

The long-term outcome and the significance of residual ischemic myocardium, as assessed by predischarge exercise thallium scintigraphy and vessel patency, were studied in 97 patients with single vessel coronary artery disease by angiography 12 +/- 4 days after uncomplicated myocardial infarction. During a mean follow-up period of 39 +/- 17 months, no patients died, 6 (6%) had a recurrent nonfatal infarction and 25 (26%) experienced rapidly progressive angina requiring hospitalization. Although neither exercise-induced angina nor ST segment depression was predictive of a recurrent cardiac event, the mean number of infarct zone scan segments showing thallium redistribution (1.0 +/- 1.0 versus 0.5 +/- 0.8, p = 0.01) and the percent of patients with infarct zone redistribution (61 versus 39%, p = 0.05) were greater in those patients who experienced a late ischemic event. Kaplan-Meier analysis demonstrated a lower event-free survival rate in patients with redistribution (n = 45) than in those without redistribution (n = 52) (p = 0.019). Although no patient received immediate thrombolytic therapy, the infarct-related vessel was angiographically patent in 40 patients (41%). Vessel patency did not influence event-free survival, although a patent vessel, as compared with an occluded vessel, was associated with a greater prevalence of non-Q wave infarction (58 versus 21%, p less than 0.001), fewer persistent infarct zone thallium defects (1.2 +/- 1.1 versus 2.0 +/- 1.2, p = 0.001), more reversible infarct zone thallium defects (1.0 +/- 1.0 versus 0.5 +/- 0.9, p = 0.02) and a trend toward a higher left ventricular ejection fraction (53 +/- 10% versus 49 +/- 12%, p = 0.07). In summary, uncomplicated myocardial infarction in patients with single vessel coronary artery disease is associated with a very low incidence of subsequent death and reinfarction. The presence of infarct zone thallium redistribution, compared with its absence, is predictive of a higher cardiac event rate. These data should be considered when recommending prophylactic percutaneous transluminal angioplasty after uncomplicated myocardial infarction in asymptomatic patients with single vessel coronary disease. On the basis of these results, future randomized trials designed to evaluate the therapeutic efficacy of revascularization in asymptomatic postinfarction patients with single vessel disease should limit enrollment to those patients with residual ischemia located within the infarct zone.

Acute non-Q wave myocardial infarction associated with early ST segment elevation: evidence for spontaneous coronary reperfusion and implications for thrombolytic trials.

The clinical significance of early ST segment elevation in patients with non-Q wave infarction is unknown. Therefore, 150 consecutive patients with creatine kinase isoenzyme-confirmed acute uncomplicated myocardial infarction who had ST segment elevation of 1 mm or more in at least two contiguous leads on the admission electrocardiogram were analyzed. None received thrombolytic therapy or acute coronary angioplasty. Predischarge angiography, radionuclide ventriculography and exercise thallium-201 scintigraphy were performed 10 +/- 3 days after myocardial infarction. Based on serial electrocardiograms (on days 1, 2, 3 and 10), all 150 infarcts were classified as Q wave (n = 115 [77%]) or non-Q wave (n = 35 [23%]). Although patients with Q wave infarction exhibited greater ST elevation, the amount observed in the non-Q wave group was appreciable, as reflected by the number of leads with ST elevation (3.8 +/- 1.8 versus 3.1 +/- 1.2, p = 0.007) and the sum of the ST elevation (9.6 +/- 7.4 versus 6.2 +/- 6.2 mm, p = 0.016). When compared with the Q wave group, patients with non-Q wave infarction had a shorter time to peak creatine kinase (23.0 +/- 9.1 versus 15.8 +/- 7.9 hours, p = 0.0001), a higher infarct vessel patency rate (24 versus 57%, p = 0.001), lower peak creatine kinase values based on 4 hour sampling (1,372 +/- 964 versus 664 +/- 924 IU/liter, p = 0.0002) and a higher left ventricular ejection fraction (46 +/- 12% versus 54 +/- 9%, p = 0.0003).(ABSTRACT TRUNCATED AT 250 WORDS)

Idiopathic ventricular tachycardia. An intracardiac electrical, hemodynamic and angiographic assessment of six patients.

Six patients with idiopathic paroxysmal ventricular tachycardia were investigated by external electrocardiography, intracardiac electrography and pacing, exercise testing, cardiac catheterization and coronary angiography. All had normal hemodynamics and coronary arteries. His bundle electrography proved ventricular origin in five; one had no paroxysmal ventricular tachycardia during His bundle electrography. Treatment with diphenylhydantoin, 4.2 to 8.0 mg/kg/day, and propranolol, 0.8 to 2.7 mg/kg/day, appeared effective, well tolerated therapy in three, and procainamide and propranolol in one requiring medical treatment. Abstinence from tobacco and coffee abolished paroxysmal ventricular tachycardia in one of two who required no medication. The other has no recurrence of paroxysmal ventricular tachycardia since study.

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.

Relation of therapeutic response to nifedipine to coronary anatomy and motion of S-T segment during unstable angina pectoris.

Of 77 patients hospitalized for unstable angina pectoris and failure of oral, dermal, or intravenous nitrates and/or beta blockade, 81 percent with negligible or single-vessel disease and 55 percent with two- or three-vessel disease showed response (p less than 0.05) to nifedipine therapy. Patients with either S-T elevation or no change during pain responded better (31 of 45) than those with any S-T depression (16 of 32; p less than 0.05). Patients with negligible or single-vessel disease had a higher prevalence of S-T elevation (13 of 16) than patients with two- or three-vessel disease (15 of 31; p = 0.004). S-T motion did not predict response in patients with two- or three-vessel disease, but did predict response in patients with negligible or single-vessel disease. On follow-up study at 9 +/- 8 (range one to 33) months, 39 of 42 who had shown response were free from pain. Three died from infarction without unstable angina. (range one to 33) months, 39 of 42 who had shown response were free from pain. Three died from infarction without unstable angina. Five who showed response had elective bypass surgery. The addition of nifedipine abolished or reduced pain episodes by more than 50 percent in 61 percent of patients with refractory unstable angina pectoris. Patients with negligible or single-vessel disease with S-T elevation benefit most. In patients with two- or three-vessel disease, the type of S-T motion did not predict response. Follow-up of all those with response indicated sustained amelioration by nifedipine therapy. Failure of nifedipine therapy should not be accepted until a dose of 120 mg per day has been achieved, or until intolerable side effects appear.

Prognostic significance of resting anterior thallium-201 defects in patients with inferior myocardial infarction.

To determine whether Tl-201 scintigraphy performed at rest during the late hospital phase of inferior myocardial infarction can predict subsequent coronary events, 25 patients with historical, enzymatic, and electrocardiographic criteria of transmural inferior infarction underwent serial imaging with computer quantification 7-35 days after admission. All 25 patients had inferior defects, and 13 (52%) also had anterior defects implying stenosis of the left anterior descending coronary artery. The patients were divided into those with inferior and anterior perfusion defects (Group 1) and those with inferior defects alone (Group 2). In Group 1, three patients had persistent defects in the anterior wall and ten had initial defects with redistribution. New or recurrent coronary events--which included new onset or progression of angina pectoris, sudden death, reinfarction, and congestive heart failure--were recorded over an average 7.2 months of followup (range 3-9 mo) for all patients. Ten of 13 (77%) patients in Group 1 had 17 coronary events and four of 12 (33%) patients in Group 2 had six coronary events (p < 0.02). Nine patients in Group 1 and three in Group 2 developed angina (p < 0.03). The apparently increased prevalence in Group 1 of sudden death (8% against 0%), reinfarction (8% against 0%), and congestive heart failure (46% against 25%) was not statistically significant. Thus resting Tl-201 scintigraphy with computer quantification is a highly sensitive method to detect inferior myocardial infarction even in the late hospital phase. Moreover, it appears to identify those patients with inferior infarction at high risk for subsequent coronary events, presumably due to stenosis of the left anterior descending coronary artery.

Analysis of pacemaker malfunction and complications of temporary pacing in the coronary care unit.

The medical records of 100 patients who received 113 temporary transvenous pacemakers were reviewed to determine the incidence of complications and malfunction. Malfunction, defined as failure to capture or sense, or both, occurred in 42 (37 percent) of 113 temporary pacemakers. The initial malfunction occurred within 24 hours in 21 (50 percent) and within 48 hours in 36 (86 percent) of the 42 pacemakers. Although the incidence of malfunction was not significantly different for brachial and femoral venous pacing catheters, 7 (37 percent) of 19 brachial venous pacemakers required repositioning or replacement compared with 8 (9 percent) of 91 femoral venous catheters (p = 0.005). Thirty-seven complications occurred in 23 (20 percent) of 113 episodes of pacing; ventricular tachycardia during catheter insertion, fever and phlebitis were the most common complications. No complication resulted in death. The incidence of complications and perforation was greater for brachial than for femoral venous pacemakers (p less than 0.05). Sepsis, local infection and pulmonary embolus occurred only with femoral venous pacemakers. Sepsis, phlebitis and pulmonary embolus were more common with temporary pacemakers in place for 7 hours or longer (p = 0.04). Recognition to the problems peculiar to each pacing catheter site and shortening the duration of pacing should help minimize problems with temporary pacing.

Influence of magnesium ion on human ventricular defibrillation after aortocoronary bypass surgery.

The administration of magnesium ion (Mg++) has been reported to defibrillate the ventricles and to decrease the incidence of arrhythmias after cardiopulmonary bypass. In a prospective study of 76 randomly selected patients undergoing coronary artery bypass grafting, patients received either no Mg++, 0.25 mEq/kg of Mg++ during cardiopulmonary bypass with the aorta clamped, or 0.375 mEq/kg of Mg++ before cardiopulmonary bypass. Spontaneous resumption of a cardiac rhythm or spontaneous defibrillation during reperfusion was not significantly affected by Mg++ administration. However, the number of shocks to initial and to sustained defibrillation and the energy required for the last direct-current shock was greatest in patients who received Mg++ before bypass and in those whose plasma Mg++ was greater than 2.26 mg/dl. Thus, the administration of Mg++ may have adverse effects on the heart if intraoperative plasma Mg++ exceeds 2.26 mg/dl.

Determinants of reperfusion cardiac electrical activity after cold cardioplegic arrest during coronary bypass surgery.

In a prospective study of 99 patients with coronary artery disease, reperfusion of the heart after a period of ischemia (protected by contemporary techniques of myocardial preservation) resulted in spontaneous resumption of cardiac electrical activity in 53%, spontaneous defibrillation in 10%, reperfusion ventricular fibrillation (VF) in 32% and indeterminate rhythm in 5%. In hearts spontaneously developing rhythms excluding VF (as opposed to hearts requiring direct-current shock), factors significantly associated were a higher plasma potassium concentration (5.2 vs 4.8 mEq/liter), shorter reperfusion time (1 vs 4 minutes), higher plasma magnesium concentration (1.36 vs 1.25 mg/dl) and a lower myocardial temperature (27 vs 32 degrees C). The duration of ischemia, arterial blood gas levels, plasma catecholamine levels, plasma ionized calcium levels, volume of cardioplegia and mean arterial pressure did not relate to occurrence of spontaneous episodes. However, VF developed in 39 of 52 patients (75%) with spontaneous resumption of electrical activity. This event was associated with lower myocardial temperature. Thus, direct-current shocks were ultimately required in 77 of the 99 patients (78%). Although certain thermal, biochemical and hemodynamic variables facilitate spontaneous resumption of cardiac rhythm, the development of VF may negate the potential benefit of this event in the prevention of myocardial damage from direct-current defibrillation.

Predicting the extent and location of coronary artery disease during the early postinfarction period by quantitative thallium-201 scintigraphy.

The ability of quantitative thallium-201 scintigraphy to predict the extent and location of coronary artery disease before hospital discharge after acute myocardial infarction was evaluated in 52 patients. All patients underwent coronary angiography and serial thallium-201 imaging either at rest (10 patients) or after submaximal exercise stress (42 patients; target heart rate 120 beats/min). Two or three vessel disease was designated if abnormal thallium-201 uptake or washout patterns, or both, were seen in two or three vascular segments, respectively. Of 156 vessels analyzed in the 52 patients, 91 stenoses of 70 percent or greater were found by angiography. Seventy-four (81 percent) of these were predicted by scintigraphy. The specificity of scintigraphy for identifying vessel stenoses was 92 percent. Sensitivity for detecting and localizing stenoses supplying an infarct zone was 96 percent compared with 62 percent for stenoses supplying myocardium remote from the acute infarct. Perfusion abnormalities were more frequently seen in the distribution of vessels with severe (90 percent or greater) stenoses than in those with moderate (70 to 90 percent) stenoses (87 versus 53 percent, p less than 0.01). Scintigraphy detected a greater proportion of left anterior descending and right coronary arterial stenoses than circumflex stenoses (91 and 87 versus 63 percent, respectively, p less than 0.006). In the 42 patients who underwent submaximal exercise testing, multivariate analysis of 23 clinical and laboratory variables identified multiple thallium-201 defects as the best predictor of multivessel disease. The predictive accuracy of exercise-induced S-T segment depression was only 45 percent compared with 88 percent (p less than 0.05) for thallium-201 scintigraphy. Thus, 2 weeks after myocardial infarction, exercise thallium-201 scintigraphy is useful for predicting the extent and location of coronary artery disease, particularly stenoses in the left anterior descending and right coronary arteries. Moreover, thallium-201 imaging at rest is reliable in assessing the extent of coronary disease in hospitalized patients who cannot undergo exercise testing because of unstable angina, uncompensated heart failure, poorly controlled arrhythmias or physical limitations.

Resection of acute posterior ventricular aneurysm with repair of ventricular septal defect after acute myocardial infarction.

Three patients with true posterior myocardial infarctions and ventricular septal defects were treated by posterior infarctectomy, closure of the defect, and appropriate combinations of mitral valve replacement and coronary grafting. Aortic balloon pumping was not used. The technique of infarctectomy and ventricular septal defect closure is illustrated. Two of the 3 patients have excellent long-term results.

Effects of coronary grafting technique upon reperfusion cardiac rhythm, ventricular function, and other variables.

The effects of different techniques of aortocoronary bypass grafting on reperfusion cardiac rhythm and ventricular function have not been systematically evaluated for possible advantages or disadvantages. The placement of proximal anastomoses before cardiopulmonary bypass and sequential coronary grafting with reperfusion via both the grafts and the native circulation were prospectively compared to traditional grafting and reperfusion via native arteries. More than 40 biochemical, thermal, temporal, hemodynamic, and other variables, including arrhythmias and myocardial failure, were measured intraoperatively and postoperatively. Spontaneous resumption of a cardiac rhythm occurred more frequently with traditional grafting technique in association with a larger cardioplegia volume and a higher serum potassium. However, the disadvantage of the traditional technique was a higher incidence of cardiac failure postoperatively and greater use of isoproterenol after discontinuation of bypass. While cardiac rhythm resumed spontaneously more often with the traditional technique, the increased incidence of cardiac failure postoperatively has serious implications. Thus, placement of proximal anastomoses before cardiopulmonary bypass seems warranted.

Syncope, Bradycardia, and Hypotension After a Lacrosse Shot to the Neck.

In brief: A lacrosse goalie was hit in the right neck lateral to the cricoid cartilage. He fainted, but responded to conservative measures of supine rest, elevated legs, and close observation. He now wears a neck protector similar to those worn by baseball catchers. This case report emphasizes that someone who is trained in basic life support and understands cardiovascular physiology should attend practices and games.