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Sudden death in noncoronary heart disease is associated with delayed paced ventricular activation
strengths, the evidence that CRT was of clinical benefit is very strong. FM
term outcomes were determined during a mean follow-up of 4.8 years. Quality of life was measured in a subgroup of 50 patients. Two control groups were used for survival comparisons: an age- and sex-matched population and an age-, sex- and disease-matched population. Results: Of the 200 patients with VF, 72% survived to hospital admission, and 40% were neurologically intact at the time of hospital discharge. Most patients were treated with revascularization, an implantable defibrillator and/or amiodarone. Among the 84 patients who survived to hospital discharge, the 5-year survival rate was 79%, which did not differ significantly from the survival in age-, sex- and disease-matched controls but was lower than the 86% 5-year survival rate in the age- and sex-matched general population. Quality of life was no different than in the general population, except for a greater degree of fatigue. Conclusions: Patients with VF who undergo early defibrillation and survive to the point of hospital discharge have a long-term survival rate that is as good as that of diseasematched controls. Quality of life in the survivors is almost as good as in the general population. Perspective: It is difficult to know to what extent the favorable long-term outcomes were attributable to early defibrillation vs. therapies such as revascularization and the implantable defibrillator. In any case, the results of the study validate an aggressive approach to out-of-hospital VF. FM
Nonsurgical Transthoracic Epicardial Radiofrequency Ablation. An Alternative in Incessant Ventricular Tachycardia Brugada J, Berruezo A, Cuesta A, et al. J Am Coll Cardiol 2003; 41:2036 – 43. Study Question: How effective is epicardial radiofrequency catheter ablation for incessant ventricular tachycardia (VT)? Methods: In 10 patients with drug-refractory incessant VT in whom endocardial ablation was ineffective or not feasible, a mapping/ablation catheter with a 4- or 8-mm tip was introduced into the pericardial space using a transthoracic subxyphoid approach. Conventional mapping criteria were used to identify appropriate epicardial target sites for ablation. Applications of radiofrequency energy were limited to 65° and 40 watts. Coronary angiography was performed to ascertain whether ablation sites were in proximity to a coronary artery. Results: The mean age of the patients was 68 years. Eight patients had coronary artery disease, one had a dilated cardiomyopathy and one had idiopathic ventricular tachycardia. The incessant VT, which had a mean cycle length of 417 ms, was successfully ablated in 8/10 patients. All ablation sites were on the left ventricular epicardium, and none was near a coronary artery. There were no complications. During a mean of 18 months of follow-up, none of the successfully ablated VTs recurred. Conclusions: Incessant VT that is not ablatable using a standard approach often can be successfully ablated by radiofrequency ablation within the pericardial space. Perspective: In patients with coronary artery disease, the VT circuit is usually endocardial and amenable to conventional radiofrequency catheter ablation. However, in 10 – 35% of patients, successful ablation cannot be achieved endocardially. This study demonstrates that epicardial mapping/ablation should be considered if a suitable endocardial ablation site for monomorphic VT cannot be identified. FM
Sudden Death in Noncoronary Heart Disease Is Associated With Delayed Paced Ventricular Activation Saumarez RC, Chojnowska L, Derksen R, et al. Circulation 2003; 107:2595– 600. Study Question: Fractionation of electrograms indicates slowed conduction that may provide a functional substrate for arrhythmias. This study determined whether fractionation of ventricular electrograms is associated with ventricular fibrillation (VF) in patients with noncoronary heart disease (NCHD). Methods: The maximum increase in electrogram duration (⌬ED) in response to a ventricular extrastimulus was measured at multiple locations in the right ventricle in 61 patients with NCHD and prior VF, 205 patients with NCHD and no history of VF, and 12 healthy control subjects. The extrastimulus interval below which the electrogram duration increased (S1S2delay) was noted. Results: The ⌬ED and the S1S2delay in patients with hypertrophic cardiomyopathy, dilated cardiomyopathy and long-QT syndrome were significantly greater among the patients with prior VF than among those without prior VF. Among patients with idiopathic VF, the ⌬ED and the S1S2delay were prolonged at some areas in the right ventricle and within normal limits in other areas.
Long-Term Outcomes of Out-of-Hospital Cardiac Arrest After Successful Early Defibrillation Bunch TJ, White RD, Gersh BJ, et al. N Engl J Med 2003;348: 2626 –33. Study Question: What is the impact of early defibrillation on long-term survival and quality of life? Methods: The subjects of this study were 200 patients with out-of-hospital ventricular fibrillation (VF) who underwent early defibrillation by police, firefighters or paramedics using an automatic external defibrillator. Short- and long-
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Usefulness of Microvolt T-Wave Alternans for Prediction of Ventricular Tachyarrhythmic Events in Patients With Dilated Cardiomyopathy From A Prospective Observational Study
Conclusions: Among patients with NCHD, fractionation of ventricular electrograms discriminates those who have had VF from those who have not. Therefore, measures of fractionation may be useful for risk stratification in NCHD. Perspective: Although this cross-sectional study demonstrated distinct differences in electrogram characteristics between patients with and without a history of VF, only a longitudinal study that examines long-term outcomes can determine whether fractionated electrograms are predictive of VF. There are problems that may limit the predictive value of fractionated electrograms. Because patients with NCHD may live for many years before dying from VF and because the disease process in many patients is progressive as opposed to static, it seems unlikely that fractionated electrograms measured at one point in time will accurately identify all or most patients who will eventually experience VF. FM
Hohnloser SH, Klingenheben T, Bloomfield D, Dabbous O, Cohen RJ. J Am Coll Cardiol 2003;41:2220 – 4. Study Question: Is microvolt T-wave alternans (MTWA) useful for risk stratification in patients with dilated cardiomyopathy (DCM)? Methods: The subjects of this study were 137 patients (mean age 55 years) with DCM (mean EF 0.29) who were in sinus rhythm. MTWA was measured during bicycle exercise. The patients also underwent determination of the ejection fraction (EF), heart rate variability (HRV), mean 24-hour heart rate, presence of nonsustained ventricular tachycardia (VT), baroreflex sensitivity (BRS) and signal-averaged electrocardiogram (SAECG). The end points of the study were sudden death, cardiac arrest due to ventricular fibrillation (VF) or sustained VT/VF documented with an implantable defibrillator (ICD). An ICD was implanted in 27% of patients with suspected or documented VT/VF. The mean duration of follow-up was 14 months. Results: MTWA was present in 48% of patients, absent in 25% and indeterminate in 27%. Among the various risk stratifiers, the only independent predictor of arrhythmic events was MTWA. Arrhythmia-free survival at 18 months was 93% when MTWA was absent, compared to 78% when MTWA was present. The positive and negative predictive values of MTWA were 22% and 94%, respectively. Conclusions: Among several potential risk stratifiers such as EF, HRV and the SAECG, the strongest predictor of VT/VF in patients with DCM is MTWA. Perspective: The results suggest that an ICD should be implanted if MTWA is present. But what if MWTA is absent? Note that the mean duration of follow-up was only 14 months, that patients with atrial fibrillation were excluded and that MTWA was indeterminate in 27% of patients. Furthermore, inclusion of very high-risk patients with a history of VT/VF created a bias in favor of MTWA. For these reasons, it is premature to use MTWA as the basis for deciding whether or not a patient with DCM should receive an ICD. FM
Modulating Effects of Age and Gender on the Clinical Course of Long QT Syndrome by Genotype Zareba W, Moss AJ, Locati EH, et al., for the International Long QT Syndrome Registry. J Am Coll Cardiol 2003;42:103–9. Study Question: What are the interactions between age, gender and genotype in patients with the congenital long QT syndrome (LQTS)? Methods: The subjects of this study were 243 patients with the LQT1 genotype of LQTS, 209 patients with the LQT2 genotype and 81 patients with the LQT3 genotype. The primary end point of the study was cardiac events (syncope, cardiac arrest, sudden death), before the initiation of therapy with beta-blockers. Cardiac events in 1075 directly related family members also were analyzed. Results: In children under the age of 16 years, LQT1 males were more likely than LQT1 females to have a cardiac event (hazard ratio 1.7), whereas gender did not influence the risk of cardiac events in LQT2 or LQT3 individuals. In contrast, among adults, women with LQT1 and LQT2 were approximately 3.5 times more likely than their male counterparts to have a cardiac event. The greatest risk of a fatal event occurred in males and females with LQT3 (18 –19%), followed by males with LQTS1 and LQTS2 (5– 6%), then by females with LQT1 and LQT2 (2%). Conclusions: The influence of age and gender on outcomes in untreated patients with LQTS varies with the specific genotype. Perspective: This is another in a series of important studies stemming from the International Long QT Syndrome Registry. An important clinical implication of the study is that prophylactic therapy, perhaps with an implantable defibrillator, may be appropriate in patients at highest risk of a fatal event, namely men and women with LQT3. FM
Development and Prospective Validation of a Risk Stratification System For Patients With Syncope in the Emergency Department: The OESIL Risk Score Colivicchi F, Ammirati F, Melina D, Guido V, Imperoli G, Santini M, for the OESIL (Osservatorio Epidemiologico Epidemiologico sulla Sincope nel Lazio) Study Investigators. Eur Heart J 2003; 24:811–9. Study Question: Are there simple clinical variables that are useful for risk stratification in patients presenting with syncope?
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term outcomes were determined during a mean follow-up of 4.8 years. Quality of life was measured in a subgroup of 50 patients. Two control groups were used for survival comparisons: an age- and sex-matched population and an age-, sex- and disease-matched population. Results: Of the 200 patients with VF, 72% survived to hospital admission, and 40% were neurologically intact at the time of hospital discharge. Most patients were treated with revascularization, an implantable defibrillator and/or amiodarone. Among the 84 patients who survived to hospital discharge, the 5-year survival rate was 79%, which did not differ significantly from the survival in age-, sex- and disease-matched controls but was lower than the 86% 5-year survival rate in the age- and sex-matched general population. Quality of life was no different than in the general population, except for a greater degree of fatigue. Conclusions: Patients with VF who undergo early defibrillation and survive to the point of hospital discharge have a long-term survival rate that is as good as that of diseasematched controls. Quality of life in the survivors is almost as good as in the general population. Perspective: It is difficult to know to what extent the favorable long-term outcomes were attributable to early defibrillation vs. therapies such as revascularization and the implantable defibrillator. In any case, the results of the study validate an aggressive approach to out-of-hospital VF. FM
Nonsurgical Transthoracic Epicardial Radiofrequency Ablation. An Alternative in Incessant Ventricular Tachycardia Brugada J, Berruezo A, Cuesta A, et al. J Am Coll Cardiol 2003; 41:2036 – 43. Study Question: How effective is epicardial radiofrequency catheter ablation for incessant ventricular tachycardia (VT)? Methods: In 10 patients with drug-refractory incessant VT in whom endocardial ablation was ineffective or not feasible, a mapping/ablation catheter with a 4- or 8-mm tip was introduced into the pericardial space using a transthoracic subxyphoid approach. Conventional mapping criteria were used to identify appropriate epicardial target sites for ablation. Applications of radiofrequency energy were limited to 65° and 40 watts. Coronary angiography was performed to ascertain whether ablation sites were in proximity to a coronary artery. Results: The mean age of the patients was 68 years. Eight patients had coronary artery disease, one had a dilated cardiomyopathy and one had idiopathic ventricular tachycardia. The incessant VT, which had a mean cycle length of 417 ms, was successfully ablated in 8/10 patients. All ablation sites were on the left ventricular epicardium, and none was near a coronary artery. There were no complications. During a mean of 18 months of follow-up, none of the successfully ablated VTs recurred. Conclusions: Incessant VT that is not ablatable using a standard approach often can be successfully ablated by radiofrequency ablation within the pericardial space. Perspective: In patients with coronary artery disease, the VT circuit is usually endocardial and amenable to conventional radiofrequency catheter ablation. However, in 10 – 35% of patients, successful ablation cannot be achieved endocardially. This study demonstrates that epicardial mapping/ablation should be considered if a suitable endocardial ablation site for monomorphic VT cannot be identified. FM
Sudden Death in Noncoronary Heart Disease Is Associated With Delayed Paced Ventricular Activation Saumarez RC, Chojnowska L, Derksen R, et al. Circulation 2003; 107:2595– 600. Study Question: Fractionation of electrograms indicates slowed conduction that may provide a functional substrate for arrhythmias. This study determined whether fractionation of ventricular electrograms is associated with ventricular fibrillation (VF) in patients with noncoronary heart disease (NCHD). Methods: The maximum increase in electrogram duration (⌬ED) in response to a ventricular extrastimulus was measured at multiple locations in the right ventricle in 61 patients with NCHD and prior VF, 205 patients with NCHD and no history of VF, and 12 healthy control subjects. The extrastimulus interval below which the electrogram duration increased (S1S2delay) was noted. Results: The ⌬ED and the S1S2delay in patients with hypertrophic cardiomyopathy, dilated cardiomyopathy and long-QT syndrome were significantly greater among the patients with prior VF than among those without prior VF. Among patients with idiopathic VF, the ⌬ED and the S1S2delay were prolonged at some areas in the right ventricle and within normal limits in other areas.
Long-Term Outcomes of Out-of-Hospital Cardiac Arrest After Successful Early Defibrillation Bunch TJ, White RD, Gersh BJ, et al. N Engl J Med 2003;348: 2626 –33. Study Question: What is the impact of early defibrillation on long-term survival and quality of life? Methods: The subjects of this study were 200 patients with out-of-hospital ventricular fibrillation (VF) who underwent early defibrillation by police, firefighters or paramedics using an automatic external defibrillator. Short- and long-
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Usefulness of Microvolt T-Wave Alternans for Prediction of Ventricular Tachyarrhythmic Events in Patients With Dilated Cardiomyopathy From A Prospective Observational Study
Conclusions: Among patients with NCHD, fractionation of ventricular electrograms discriminates those who have had VF from those who have not. Therefore, measures of fractionation may be useful for risk stratification in NCHD. Perspective: Although this cross-sectional study demonstrated distinct differences in electrogram characteristics between patients with and without a history of VF, only a longitudinal study that examines long-term outcomes can determine whether fractionated electrograms are predictive of VF. There are problems that may limit the predictive value of fractionated electrograms. Because patients with NCHD may live for many years before dying from VF and because the disease process in many patients is progressive as opposed to static, it seems unlikely that fractionated electrograms measured at one point in time will accurately identify all or most patients who will eventually experience VF. FM
Hohnloser SH, Klingenheben T, Bloomfield D, Dabbous O, Cohen RJ. J Am Coll Cardiol 2003;41:2220 – 4. Study Question: Is microvolt T-wave alternans (MTWA) useful for risk stratification in patients with dilated cardiomyopathy (DCM)? Methods: The subjects of this study were 137 patients (mean age 55 years) with DCM (mean EF 0.29) who were in sinus rhythm. MTWA was measured during bicycle exercise. The patients also underwent determination of the ejection fraction (EF), heart rate variability (HRV), mean 24-hour heart rate, presence of nonsustained ventricular tachycardia (VT), baroreflex sensitivity (BRS) and signal-averaged electrocardiogram (SAECG). The end points of the study were sudden death, cardiac arrest due to ventricular fibrillation (VF) or sustained VT/VF documented with an implantable defibrillator (ICD). An ICD was implanted in 27% of patients with suspected or documented VT/VF. The mean duration of follow-up was 14 months. Results: MTWA was present in 48% of patients, absent in 25% and indeterminate in 27%. Among the various risk stratifiers, the only independent predictor of arrhythmic events was MTWA. Arrhythmia-free survival at 18 months was 93% when MTWA was absent, compared to 78% when MTWA was present. The positive and negative predictive values of MTWA were 22% and 94%, respectively. Conclusions: Among several potential risk stratifiers such as EF, HRV and the SAECG, the strongest predictor of VT/VF in patients with DCM is MTWA. Perspective: The results suggest that an ICD should be implanted if MTWA is present. But what if MWTA is absent? Note that the mean duration of follow-up was only 14 months, that patients with atrial fibrillation were excluded and that MTWA was indeterminate in 27% of patients. Furthermore, inclusion of very high-risk patients with a history of VT/VF created a bias in favor of MTWA. For these reasons, it is premature to use MTWA as the basis for deciding whether or not a patient with DCM should receive an ICD. FM
Modulating Effects of Age and Gender on the Clinical Course of Long QT Syndrome by Genotype Zareba W, Moss AJ, Locati EH, et al., for the International Long QT Syndrome Registry. J Am Coll Cardiol 2003;42:103–9. Study Question: What are the interactions between age, gender and genotype in patients with the congenital long QT syndrome (LQTS)? Methods: The subjects of this study were 243 patients with the LQT1 genotype of LQTS, 209 patients with the LQT2 genotype and 81 patients with the LQT3 genotype. The primary end point of the study was cardiac events (syncope, cardiac arrest, sudden death), before the initiation of therapy with beta-blockers. Cardiac events in 1075 directly related family members also were analyzed. Results: In children under the age of 16 years, LQT1 males were more likely than LQT1 females to have a cardiac event (hazard ratio 1.7), whereas gender did not influence the risk of cardiac events in LQT2 or LQT3 individuals. In contrast, among adults, women with LQT1 and LQT2 were approximately 3.5 times more likely than their male counterparts to have a cardiac event. The greatest risk of a fatal event occurred in males and females with LQT3 (18 –19%), followed by males with LQTS1 and LQTS2 (5– 6%), then by females with LQT1 and LQT2 (2%). Conclusions: The influence of age and gender on outcomes in untreated patients with LQTS varies with the specific genotype. Perspective: This is another in a series of important studies stemming from the International Long QT Syndrome Registry. An important clinical implication of the study is that prophylactic therapy, perhaps with an implantable defibrillator, may be appropriate in patients at highest risk of a fatal event, namely men and women with LQT3. FM
Development and Prospective Validation of a Risk Stratification System For Patients With Syncope in the Emergency Department: The OESIL Risk Score Colivicchi F, Ammirati F, Melina D, Guido V, Imperoli G, Santini M, for the OESIL (Osservatorio Epidemiologico Epidemiologico sulla Sincope nel Lazio) Study Investigators. Eur Heart J 2003; 24:811–9. Study Question: Are there simple clinical variables that are useful for risk stratification in patients presenting with syncope?
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