- Email: [email protected]
Left septal atrial flutter. Electrophysiology, anatomy, and results of ablation
gender-matched controls. During follow-up, AF/Fl was documented by Holter monitoring or implantable cardioverter-defibrillator (ICD) stored electrograms. Results: Electrophysiologic testing demonstrated that, in comparison to controls, patients with BS had a higher incidence of sinus node dysfunction (17% vs. 0%), an HV interval ⬎55 ms (21% vs. 0%), and inducible ventricular tachycardia (35% vs. 0%). During a median follow-up of 32 months, AF/Fl occurred in 20% of BS patients, compared to no events in controls. During follow-up, AF/Fl was associated with a typical BS pattern on baseline electrocardiogram, a prolonged HV interval, and with the inducibility of ventricular tachycardia by programmed ventricular stimulation. Conclusions: Atrial arrhythmias are part of the BS and may indicate a more severe form of the syndrome. Perspective: The BS is caused by a mutation in the SCN5A gene that affects cardiac sodium channels. Because sodium channel function affects the electrophysiology of not only the ventricle but also the sinus node, atrium and HisPurkinje system, it is not surprising that sinus node dysfunction, AF/Fl, and prolongation of the HV interval may occur in the BS. Because AF/Fl appears to indicate a more severe form of the BS, an important implication of the study is that AF/Fl at the time of presentation may be an indication for ICD implantation. FM
for identifying those who are at high risk of sudden death. This study indicates that a BS pattern has no prognostic significance and may be simply a normal variant, at least in a Northern European population. It should be kept in mind that the results may not apply to individuals with coved ST-segment elevation, or to populations (such as Southeast Asians) with a relatively high prevalence of BS. FM
Clinical Correlates and Prognostic Significance of Exercise-Induced Ventricular Premature Beats in the Community. The Framingham Heart Study Morshedi-Meibodi A, Evans JC, Levy D, Larson MG, Vasan RS. Circulation 2004;109:2417–22. Study Question: Are exercise-induced ventricular premature beats (EPVBs) associated with an increased risk of coronary heart disease (CHD) events or all-cause mortality? Methods: The subjects of this study were 2885 apparently healthy individuals (mean age 43 years, 48% males) in the Framingham Heart Study who underwent an exercise treadmill test. EPVBs were classified as infrequent (ⱕmedian) or frequent (⬎median). CHD events (myocardial infarction, coronary insufficiency, CHD death) and allcause mortality were evaluated during a mean of 15 years. Results: The EPVBs occurred in 27% of subjects, at a mean rate of 0.22/min, and were related to age and male gender. EPVBs were associated with all-cause mortality (hazard ratio 1.8), but not with CHD events. The relationship of EPVBs to all-cause mortality was independent of the frequency or complexity of ventricular ectopy, left ventricular dysfunction, and an ischemic ST-segment response. Conclusions: In apparently healthy and asymptomatic individuals, EPVBs are associated with an increased risk of all-cause mortality. Perspective: Prior studies have been evenly split on the issue of whether EPVBs have any prognostic significance. Additional studies such as the present one therefore are helpful; it is hoped they will create a majority consensus on this issue. Assuming that EPVBs actually are associated with an increased risk of all-cause mortality, a critical question that is unanswered is whether suppression of EPVBs improves prognosis. Given the results of the CAST study, it would seem unwise to treat patients who have EPVBs with any antiarrhythmic agent other than a beta-blocker. FM
Prevalence and Prognosis of Subjects With Brugada-type ECG Pattern in a Young and MiddleAged Finnish Population Junttila MJ, Raatikainen MJP, Karjalainen J, Kauma H, Kesaniemi YA, Huikuri HV. Eur Heart J 2004;25:874 – 8. Study Question: How often is a Brugada syndrome (BS) pattern seen in healthy individuals in Finland, and what is the natural history of individuals who have the pattern? Methods: Electrocardiographic screening was performed in 2479 male air force recruits (ages 18 –30 years) and 542 healthy subjects (ages 40 – 60 years, 274 males). The BS pattern was defined as coved (type I) or saddleback (type II or III) ST-segment elevation in leads V1 through V3. Follow-up information was obtained after a mean of 19 years in the recruits and 11 years in the middle-aged subjects. Results: The prevalence of the BS pattern was 0.61% in the young recruits and 0.55% in the middle-aged subjects. In all cases, there was saddleback ST-segment elevation (type II or III). At last follow-up, none of the patients with the BS pattern had experienced syncope, sudden death, or symptomatic ventricular tachycardia, and none had had any family members with sudden death. Conclusions: In asymptomatic individuals without a family history of sudden death, saddleback ST-segment elevation in leads V1 through V3 has no prognostic significance. Perspective: Some studies have suggested that screening for the BS pattern in asymptomatic individuals may be useful
High Incidence of Pacemaker Syndrome in Patients With Sinus Node Dysfunction Treated With Ventricular-Based Pacing in the Mode Selection Trial (MOST) Link MS, Hellkamp AS, Estes NAM, et al. for the MOST study investigators. J Am Coll Cardiol 2004;43:2066 –71. Study Question: What are the incidence and predictors of pacemaker syndrome (PS) in patients with sinus node dysfunction (SND) treated with ventricular (VVIR) pacing?
ACC CURRENT JOURNAL REVIEW Aug 2004
47
Methods: Among 2010 patients with SND who underwent implantation of a dual-chamber pacemaker, 996 patients (median age 74 years) were randomly assigned to VVIR pacing. PS was defined as congestive symptoms associated with ventriculoatrial (VA) conduction during VVIR pacing, or a symptomatic drop in systolic pressure of ⬎20 mm Hg during VVIR pacing. Results: The prevalence of PS was 14% at 6 months and 20% at 4 years of follow-up. In a multivariate analysis, no baseline demographic, clinical or pacemaker implant variables were predictive of PS. A high percentage of paced beats during follow-up was the only independent predictor of PS. Quality of life decreased in patients with PS and improved significantly after crossover to dual-chamber pacing.
Conclusions: PS occurs in 20% of patients with SND treated with VVIR pacing. Because patients who will develop PS cannot be accurately identified at the time of implantation, it may be advisable to treat all patients with atrial-based pacemakers. Perspective: In this study, crossover to dual-chamber pacing required only noninvasive reprogramming. But in older studies in which upgrade to a dual-chamber pacemaker required an additional invasive procedure to implant an atrial lead and to change the pacemaker generator, the prevalence of PS with VVIR pacing was consistently ⬍5%. It is possible that the need for another invasive procedure may inhibit patients from complaining about PS-related symptoms or may inhibit physicians from diagnosing PS. FM
ACC CURRENT JOURNAL REVIEW Aug 2004
48
for identifying those who are at high risk of sudden death. This study indicates that a BS pattern has no prognostic significance and may be simply a normal variant, at least in a Northern European population. It should be kept in mind that the results may not apply to individuals with coved ST-segment elevation, or to populations (such as Southeast Asians) with a relatively high prevalence of BS. FM
Clinical Correlates and Prognostic Significance of Exercise-Induced Ventricular Premature Beats in the Community. The Framingham Heart Study Morshedi-Meibodi A, Evans JC, Levy D, Larson MG, Vasan RS. Circulation 2004;109:2417–22. Study Question: Are exercise-induced ventricular premature beats (EPVBs) associated with an increased risk of coronary heart disease (CHD) events or all-cause mortality? Methods: The subjects of this study were 2885 apparently healthy individuals (mean age 43 years, 48% males) in the Framingham Heart Study who underwent an exercise treadmill test. EPVBs were classified as infrequent (ⱕmedian) or frequent (⬎median). CHD events (myocardial infarction, coronary insufficiency, CHD death) and allcause mortality were evaluated during a mean of 15 years. Results: The EPVBs occurred in 27% of subjects, at a mean rate of 0.22/min, and were related to age and male gender. EPVBs were associated with all-cause mortality (hazard ratio 1.8), but not with CHD events. The relationship of EPVBs to all-cause mortality was independent of the frequency or complexity of ventricular ectopy, left ventricular dysfunction, and an ischemic ST-segment response. Conclusions: In apparently healthy and asymptomatic individuals, EPVBs are associated with an increased risk of all-cause mortality. Perspective: Prior studies have been evenly split on the issue of whether EPVBs have any prognostic significance. Additional studies such as the present one therefore are helpful; it is hoped they will create a majority consensus on this issue. Assuming that EPVBs actually are associated with an increased risk of all-cause mortality, a critical question that is unanswered is whether suppression of EPVBs improves prognosis. Given the results of the CAST study, it would seem unwise to treat patients who have EPVBs with any antiarrhythmic agent other than a beta-blocker. FM
Prevalence and Prognosis of Subjects With Brugada-type ECG Pattern in a Young and MiddleAged Finnish Population Junttila MJ, Raatikainen MJP, Karjalainen J, Kauma H, Kesaniemi YA, Huikuri HV. Eur Heart J 2004;25:874 – 8. Study Question: How often is a Brugada syndrome (BS) pattern seen in healthy individuals in Finland, and what is the natural history of individuals who have the pattern? Methods: Electrocardiographic screening was performed in 2479 male air force recruits (ages 18 –30 years) and 542 healthy subjects (ages 40 – 60 years, 274 males). The BS pattern was defined as coved (type I) or saddleback (type II or III) ST-segment elevation in leads V1 through V3. Follow-up information was obtained after a mean of 19 years in the recruits and 11 years in the middle-aged subjects. Results: The prevalence of the BS pattern was 0.61% in the young recruits and 0.55% in the middle-aged subjects. In all cases, there was saddleback ST-segment elevation (type II or III). At last follow-up, none of the patients with the BS pattern had experienced syncope, sudden death, or symptomatic ventricular tachycardia, and none had had any family members with sudden death. Conclusions: In asymptomatic individuals without a family history of sudden death, saddleback ST-segment elevation in leads V1 through V3 has no prognostic significance. Perspective: Some studies have suggested that screening for the BS pattern in asymptomatic individuals may be useful
High Incidence of Pacemaker Syndrome in Patients With Sinus Node Dysfunction Treated With Ventricular-Based Pacing in the Mode Selection Trial (MOST) Link MS, Hellkamp AS, Estes NAM, et al. for the MOST study investigators. J Am Coll Cardiol 2004;43:2066 –71. Study Question: What are the incidence and predictors of pacemaker syndrome (PS) in patients with sinus node dysfunction (SND) treated with ventricular (VVIR) pacing?
ACC CURRENT JOURNAL REVIEW Aug 2004
47
Methods: Among 2010 patients with SND who underwent implantation of a dual-chamber pacemaker, 996 patients (median age 74 years) were randomly assigned to VVIR pacing. PS was defined as congestive symptoms associated with ventriculoatrial (VA) conduction during VVIR pacing, or a symptomatic drop in systolic pressure of ⬎20 mm Hg during VVIR pacing. Results: The prevalence of PS was 14% at 6 months and 20% at 4 years of follow-up. In a multivariate analysis, no baseline demographic, clinical or pacemaker implant variables were predictive of PS. A high percentage of paced beats during follow-up was the only independent predictor of PS. Quality of life decreased in patients with PS and improved significantly after crossover to dual-chamber pacing.
Conclusions: PS occurs in 20% of patients with SND treated with VVIR pacing. Because patients who will develop PS cannot be accurately identified at the time of implantation, it may be advisable to treat all patients with atrial-based pacemakers. Perspective: In this study, crossover to dual-chamber pacing required only noninvasive reprogramming. But in older studies in which upgrade to a dual-chamber pacemaker required an additional invasive procedure to implant an atrial lead and to change the pacemaker generator, the prevalence of PS with VVIR pacing was consistently ⬍5%. It is possible that the need for another invasive procedure may inhibit patients from complaining about PS-related symptoms or may inhibit physicians from diagnosing PS. FM
ACC CURRENT JOURNAL REVIEW Aug 2004
48