Positron emission tomography absolute stress myocardial blood flow for risk stratification in nonischemic cardiomyopathy.

INTRODUCTION: Sudden cardiac death is a substantial cause of mortality in patients with cardiomyopathy, but evidence supporting implantable cardioverter-defibrillator (ICD) implantation is less robust in nonischemic cardiomyopathy (NICM) than in ischemic cardiomyopathy. Improved risk stratification is needed. We assessed whether absolute quantification of stress myocardial blood flow (sMBF) measured by positron emission tomography (PET) predicts ventricular arrhythmias (VA) and/or death in patients with NICM. METHODS: In this pilot study, we prospectively followed patients with NICM (left ventricular ejection fraction ≤ 35%) and an ICD who underwent cardiac PET stress imaging with sMBF quantification. NICM was defined as the absence of angiographic obstructive coronary stenosis, significant relative perfusion defects on imaging, coronary revascularization, or acute coronary syndrome. Endpoints were appropriate device therapy for VA and all-cause mortality. Subgroup analysis was performed in patients who had no prior history of VA (ie, the primary prevention population). RESULTS: We followed 37 patients (60 ± 14 years, 46% male) for 41 ± 23 months. The median sMBF was 1.56 mL/g/min (interquartile range: 1.00-1.82). Lower sMBF predicted VA, both in the whole population (hazard ratio [HR] for each 0.1 mL/g/min increase: 0.84, P = .015) and in the primary prevention subset (n = 27; HR for each 0.1 mL/g/min increase: 0.81, P = .049). Patients with sMBF below the median had significantly more VA than those above the median, both in the whole population (P = .004) and in the primary prevention subset (P = .046). Estimated 3-year VA rates in the whole population were 67% among low-flow patients vs 13% among high-flow patients, and 39% vs 8%, respectively, among primary-prevention patients. sMBF did not predict all-cause mortality. CONCLUSIONS: In patients with NICM, lower sMBF predicts VA. This relationship may be useful for risk stratification for ventricular arrhythmia and decision making regarding ICD implantation.

Optimal method of measuring the T-peak to T-end interval for risk stratification in primary prevention.

Aims: Several published investigations demonstrated that a longer T-peak to T-end interval (Tpe) implies increased risk for ventricular tachyarrhythmia (VT/VF) and mortality. Tpe has been measured using diverse methods. We aimed to determine the optimal Tpe measurement method for screening purposes. Methods and results: We evaluated 305 patients with LVEF ≤ 35% and an implantable cardioverter-defibrillator implanted for primary prevention. Tpe was measured using seven different methods described in the literature, including six manual methods and the automated algorithm '12SL', and was corrected for heart rate. Endpoints were VT/VF and death. To account for differences in the magnitude of Tpe measurements, results are expressed in standard deviation (SD) increments. We evaluated the clinical utility of each measurement method based on predictive ability, fraction of immeasurable tracings, and intra- and interobserver correlation. >Over 31 ± 23 months, 82 (27%) patients had VT/VF, and over 49 ± 21 months, 91 (30%) died. Several rate-corrected Tpe measurement methods predicted VT/VF (HR per SD 1.20-1.34; all P < 0.05), and nearly all methods (both corrected and uncorrected) predicted death (HR per SD 1.19-1.35; all P < 0.05). Optimal predictive ability, readability, and correlation were found in the automated 12SL method and the manual tangent method in lead V2. Conclusion: For the prediction of VT/VF, the utility of Tpe depends upon the measurement method, but for the prediction of mortality, most published Tpe measurement methods are similarly predictive. Heart rate correction improves predictive ability. The automated 12SL method performs as well as any manual measurement, and among manual methods, lead V2 is most useful.

Natural History and Implantable Cardioverter-Defibrillator Implantation After Revascularization for Stable Coronary Artery Disease With Depressed Ejection Fraction.

BACKGROUND: Following revascularization, most payors require 3 months of medical therapy, followed by left ventricular ejection fraction (LVEF) reassessment, before implantable cardioverter-defibrillator (ICD) implantation possibly contributing to incomplete follow-up and suboptimal utilization of ICD therapy. The natural history of these patients, and their fate regarding ICD implantation, is unknown. HYPOTHESIS: We hypothesized that a waiting period after revascularization for stable CAD results in missed opportunities to provide care with regard to ICD implantation. METHODS: We followed patients with LVEF ≤ 35% and no ICD who underwent revascularization (coronary artery bypass grafting [CABG] or percutaneous coronary intervention [PCI]) for stable CAD. Follow-up used chart review and scripted telephone interviews. RESULTS: Among 3164 revascularized patients (2198 [69%] PCI, 966 [31%] CABG), only 62 (2%; 33 [53%] male, age 67 ± 12 y, LVEF 28% ± 6%) had stable CAD, depressed LVEF, and no ICD. Over 35 ± 19 months, 35 (56%) of these 62 patients were no longer candidates for ICD based on improved LVEF, 14 (23%) received an ICD, 5 (8%) declined ICD despite physician recommendation, 3 (5%) were not offered ICD despite continued eligibility, 2 (3%) died, 1 (2%) was not a candidate due to substance abuse, and 1 (2%) had ICD implantation temporarily deferred. Only 1 (2%) was lost to follow-up. CONCLUSIONS: Following revascularization for stable CAD with depressed LVEF, ≥50% of patients' ventricular function improved enough to make ICD implantation unnecessary. A waiting period after revascularization prior to ICD implantation appears appropriate and does not significantly negatively impact follow-up or the rate of appropriate ICD implantation.

Lifestyle modification in the prevention and treatment of atrial fibrillation.

Atrial fibrillation (AF) is the most common arrhythmia worldwide and has a significant impact on morbidity and mortality. Additionally, the incidence and prevalence of AF is expected to increase in the United States and worldwide over the next few decades. While the pathophysiology concerning the development of AF is not completely understood, multiple modifiable, as well as non-modifiable risk factors, for AF development have been discovered. The goal of this paper is to provide an overview of the modifiable risk factors that contribute to the development and recurrence of AF, in addition to discussing potential lifestyle changes that may aid in the prevention and treatment of AF.

T-peak to T-end interval for prediction of ventricular tachyarrhythmia and mortality in a primary prevention population with systolic cardiomyopathy.

BACKGROUND: The electrocardiographic T-wave peak to T-wave end interval (Tpe) correlates with dispersion of ventricular repolarization (DVR). Increased DVR increases propensity toward electrical reentry that can cause ventricular tachyarrhythmia. The baseline rate-corrected Tpe (Tpec) has been shown to predict ventricular tachyarrhythmia and death in multiple patient populations but not among cardiomyopathic patients undergoing insertion of an implantable cardioverter-defibrillator (ICD) for primary prevention. OBJECTIVE: The purpose of this study was to assess the risk stratification ability of the Tpec in patients with systolic cardiomyopathy without prior ventricular tachyarrhythmia (ie, the primary prevention population). METHODS: We performed prospective follow-up of 305 patients (73% men; left ventricular ejection fraction [LVEF] 23 ± 7%) with LVEF ≤35% and an ICD implanted for primary prevention. Baseline ECGs were analyzed with automated algorithms. Endpoints were ventricular tachycardia (VT)/ventricular fibrillation (VF), death, and a combined endpoint of VT/VF or death, assessed by device follow-up and Social Security Death Index query. RESULTS: The average Tpec was 107 ± 22 ms. During device clinic follow-up of 31 ± 23 months, 82 patients (27%) had appropriate ICD therapy for VT/VF, and during mortality follow-up of 49 ± 21 months, 91 patients (30%) died. On univariable analysis, Tpec predicted VT/VF, death, and the combined endpoint of VT/VF or death (P < .05 for each endpoint). Multivariable analysis included univariable predictors among demographics, clinical data, laboratory data, medications used, and electrocardiography parameters. After correction, Tpec remained predictive of VT/VF (hazard ratio [HR] per 10-ms increase 1.16, P = .009), all-cause mortality (HR per 10 ms 1.13, P = .05), and the combined endpoint (HR per 10 ms 1.17, P = .001). CONCLUSION: Tpec independently predicts both VT/VF and overall mortality in patients with systolic dysfunction and ICDs implanted for primary prevention.

First experience with a novel robotic remote catheter system: Amigo™ mapping trial.

INTRODUCTION: Amigo™ (Catheter Robotics, Inc., Mount Olive, NJ) remote catheter system (RCS) was designed to provide a simple and relatively inexpensive system for remote catheter manipulation. The purpose of this study was to evaluate the performance and safety of Amigo in mapping the right side of the heart. METHODS AND RESULTS: This non-randomized, prospective clinical trial was conducted at 13 sites (NCT: #01139814). Using the controller, a mapping catheter was moved to eight pre-specified locations in a specific sequence: right ventricular apex, mid-right ventricular septum, right ventricular outflow tract, His-bundle position, coronary sinus ostium, high right atrium, lateral tricuspid annulus, and low lateral right atrium. The pre-specified efficacy endpoint was to achieve 80 % successful navigation to all locations. Time to each location, location accuracy, and quality of contact were confirmed by imaging and specific criteria for electrograms and pacing thresholds. In 181 patients, a total of 1,396 of 1,448 (96 %) locations were successfully mapped with all protocol criteria met (one-sided p value < 0.0001). The median time to move the catheter to a new location was 24 s. The Amigo-related major complication rate was 0 % which was significantly less than the predefined endpoint of 4 % (one-sided p = 0.003). CONCLUSION: We found the Amigo RCS to be safe and effective for positioning a mapping catheter at sites within the right atrium and ventricle.

Effect of rate-adaptive pacing on performance and physiological parameters during activities of daily living in the elderly: results from the CLEAR (Cylos Responds with Physiologic Rate Changes during Daily Activities) study.

AIMS: For most elderly pacemaker patients, evaluation of rate-adaptive pacing using treadmill and bicycle tests is impractical and not representative of typical daily activities. This study was designed to compare the performance and physiological response of the closed-loop stimulation (CLS) rate-adaptive sensor to accelerometer (XL) and no rate sensor (DDD) during typical daily activity testing. METHODS AND RESULTS: Subjects recently implanted with a Cylos pacemaker completed timed activities of daily life testing, which included walking, sweeping, and standing from a seated position. Activity performance and physiological response from each sensor mode was evaluated for subjects requiring ≥80% pacing. Overall, 74 subjects needed ≥80% pacing during at least one test. An increase in the area swept (CLS vs. XL, 1.67 m(2) difference, P = 0.009; CLS vs. DDD, 1.59 m(2) difference, P = 0.025) and a decrease in the prevalence of orthostatic hypotension (OH) after standing 1 min (CLS vs. XL, odds ratio = 0.16, P = 0.006; CLS vs. DDD, odds ratio = 0.18, P = 0.012) was observed in the CLS mode as compared with XL and DDD. No statistical difference in walk distance was observed between CLS and XL or CLS and DDD. CONCLUSION: In acute testing, as compared with XL and DDD, CLS provides a more physiological response during the performance of activities of daily living for subjects with ≥80% pacing. This is clinically reflected in better performance during the sweep test as well as a decrease in the prevalence of OH in our elderly population. Clinicaltrials.gov identifier: NCT00355797.

Cardiometabolic risk factors and atrial fibrillation.

Atrial fibrillation (AF) is the most common arrhythmia worldwide; it is a significant risk factor for stroke and embolization, and has an impact on cardiac function. Despite its impact on morbidity and mortality, our understanding of the etiology and pathophysiology of this disease process is still incomplete. Over the past several decades, there has been evidence to suggest that AF has a significant correlation with metabolic syndrome (MetS). Furthermore, AF appears to be more closely related to specific components of MetS compared with others. This article provides an overview of the various components of MetS and their impact on AF.

Relationships between the T-peak to T-end interval, ventricular tachyarrhythmia, and death in left ventricular systolic dysfunction.

AIMS: The interval between the T-wave's peak and end (Tpe), an electrocardiographic (ECG) index of ventricular repolarization, has been proposed as an indicator of arrhythmic risk. We aimed to clarify the clinical usefulness of Tpe for risk stratification. METHODS AND RESULTS: We evaluated 327 patients with left ventricular ejection fraction (LVEF) ≤ 35% (75% male, LVEF 23 ± 7%). All patients had an implanted implantable cardioverter-defibrillator (ICD). Clinical data and ECGs were analysed at baseline. Prospective follow-up for the endpoints of appropriate ICD therapy and mortality was conducted via periodic device interrogation, chart review, and the Social Security Death Index. During device clinic follow-up of 17 ± 12 months, 59 (18%) patients had appropriate ICD therapy, and during mortality follow-up of 30 ± 13 months, 67 (21%) patients died. A longer Tpe(c) predicted appropriate ICD therapy, death, and the combination of appropriate ICD therapy or death (P< 0.01 for each endpoint). On multivariable analysis correcting for other univariable predictors, Tpe(c) remained predictive of ICD therapy [hazard ratio (HR) per 10 ms increase: 1.16, P= 0.02], all-cause mortality (HR per 10 ms: 1.14, P= 0.03), and the composite endpoint of ICD therapy or death (HR per 10 ms: 1.16, P< 0.01). CONCLUSIONS: In patients with left ventricular systolic dysfunction and an implanted ICD, Tpe(c) independently predicts both ventricular tachyarrhythmia and overall mortality.

Cardiac implantable electrical devices: bioethics and management issues near the end of life.

Cardiac implantable electrical devices (CIEDs) are extremely sophisticated modern devices that provide patients with many beneficial effects, including increased survival and enhanced quality of life. CIEDs, however, may complicate and unnecessarily prolong the process of dying from terminal illnesses. A rational plan for CIED deactivation near the end of life should therefore be carefully drawn up well in advance by the patient in concert with loved ones and treating physicians.

Long-term mortality in patients with pauses in ventricular electrical activity.

BACKGROUND: The long-term significance of ventricular pauses of > or =3.0 seconds observed on Holter monitor is unclear, as previously conducted retrospective studies have been poorly controlled. We compared the prognosis of patients with pauses > or =3.0 seconds on Holter monitor with a well-matched control group without such pauses. METHODS: Scanning the Holter database at Ochsner Clinic (n = 11,730; January 1998 to June 2003) for pauses > or =3.0 seconds identified 70 patients (pause group). Of those, 29 (37.1%) received a permanent pacemaker (PPM group) and 41 (62.9%) did not (No-PPM group). For each No-PPM patient, two patients without pauses (<2.0 seconds) exactly matched for age, sex, ejection fraction (EF), rhythm, and duration of follow-up were randomly chosen from the Holter database (control group, n = 82) and survival of the two groups was compared. RESULTS: Mean age was 72.5 +/- 15.0 years, mean EF was 52.2 +/- 12.7%, and 68.3% were men. Mean follow-up was 2.2 years (0.5-4.5 years). There was no difference in survival between the No-PPM and the control groups (82.9% vs 84.1%, P = NS). Compared with the PPM group, pauses in the No-PPM group were more commonly asymptomatic, nocturnal, and due to sinus pauses or atrial fibrillation (AF) with slow ventricular response. CONCLUSIONS: Pauses in ventricular electrical activity > or =3 seconds on Holter monitor due to sinus pauses or AF with slow ventricular response are not predictive of heightened mortality.

Relation between left ventricular geometry and transmural dispersion of repolarization.

Studies have shown an association between left ventricular (LV) geometry and complex ventricular ectopic activity. Increased transmural dispersion of repolarization (TDR), which correlates to the interval from the peak to the end of the T wave (Tpe) on the surface electrocardiogram, is linked to ventricular tachyarrhythmias. The relation between LV geometry and TDR is unknown. The mean Tpe interval, measured from leads V(1) to V(3) of the surface electrocardiogram, was assessed in 300 patients (50% men) who had normal LV systolic function and QRS duration and were categorized into 3 equal groups, which were matched by age and gender, according to echocardiographically determined LV geometry (normal structure, concentric remodeling, and LV hypertrophy). The Tpe interval was corrected for the QT interval using Tpe/QTc and was compared among the 3 groups. Compared with those who had normal LV structure, the Tpe interval was significantly prolonged in those who had LV hypertrophy and significantly shortened in those who had concentric remodeling (p = <0.0001 for the 2 comparisons). Correcting for the QT interval using Tpe/QTc yielded similar results. Thus, TDR was increased in patients who had LV hypertrophy but decreased in concentric remodeling compared with those who had normal cardiac structure. Although LV hypertrophy represents a maladaptive geometric process that results in an unfavorable electrical substrate, concentric remodeling may represent a structural adaptation that has a more favorable electrical milieu.

Repeated dual external direct cardioversions using two simultaneous 360-J shocks for refractory atrial fibrillation are safe and effective.

Failure of cardioversion of atrial fibrillation (AF) to sinus rhythm (SR) by standard external direct current cardioversion (DCC) may be due to failure of delivery of enough defibrillating energy rather than to the true refractoriness of AF. Ninety-nine patients with persistent AF (76 male; age 63.7 +/- 0.4 years; weight 113.1 +/- 25.1 kg) who failed standard DCC were included in this report. Under anesthesia, QRS synchronous shocks were delivered across anteroposterior electrodes in the following sequence: (1) a single 360-J shock; (2) another single 360-J shock within 2 minutes; (3) 30 minutes of rest, reinduction of anesthesia and delivery of two simultaneous monophasic 360-J shocks. All patients underwent all three DCC steps. Sixty-six (67%) patients converted to SR following the first dual simultaneous shock. Fourteen patients (14%) required more than one dual shock to achieve SR. This increased the overall success rate of resuming SR to 81%. Except for minor skin burns in three patients there were no procedure related complications. On follow-up at 1 month, 55 (56%) patients were still in SR, whereas 50 (51%) patients maintained SR at 12 months. This was similar to our general DCC population (55% of the 1698 patients were in SR 6 months post-DCC, P = ns). In conclusion, dual external monophasic 360-J DCC is an effective rescue technique for restoration of SR in patients with AF refractory to standard DCC. AF in these patients seems to be as amenable to chronic suppression as AF in the general population of DCC patients.

Pacing techniques in heart failure: current concepts and future outlook.

In addition to the well established benefits of traditional pacing methods, newer, left ventricular-based pacing techniques appear to induce significant hemodynamic improvements, benefit cardiac remodeling, improve functional capacity, and may decrease hospitalizations in appropriately selected patients with advanced systolic heart failure and intraventricular conduction defects. Encouraging results have been suggested from preliminary observational studies as well as from controlled clinical trials. Despite the generally positive outlook, much remains to be learned about multisite pacing techniques, appropriate site and patient selection, and long-term effectiveness.