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Biomedical subjects

Ronald D Berger

Publications and source records attributed to Ronald D Berger.

16 recordsLinked to original sources
PubMed2004

Short-term effects of right-left heart sequential cardiac resynchronization in patients with heart failure, chronic atrial fibrillation, and atrioventricular nodal block.

BACKGROUND: Single-site ventricular pacing in patients with heart failure, atrial fibrillation, and severe atrioventricular (AV) nodal block risks the generation of discoordinate contraction. Whether altering the site of stimulation can offset this detrimental effect and what role sequential right ventricular-left ventricular (RV-LV) stimulation might play in such patients remain unknown. METHODS AND RESULTS: Nine subjects with heart failure (ejection fraction, 14% to 30%), atrial fibrillation, and AV block were studied by pressure-volume analysis. Ventricular stimulation was applied to the RV (apex and outflow tract), LV free wall, and biventricular (BiV) at 80 and 120 bpm. BiV improved systolic function more than either site alone (dP/dt(max), 810+/-83, 924+/-98, 983+/-102 mm Hg/s for RV, LV, BiV, respectively; P<0.05), although LV pacing was significantly better than RV pacing. However, only BiV improved diastolic function (isovolumic relaxation) over RV or LV alone. Similar results were obtained for both heart rates. RV pacing site did not alter the BiV effect, and concomitant stimulation of both RV sites did not improve function over each alone. Finally, varying RV-LV delay revealed optimal responses with simultaneous pacing. CONCLUSIONS: Simultaneous BiV pacing acutely enhances both systolic and diastolic function over single-site RV or LV pacing in congestive heart failure patients with atrial fibrillation and advanced AV block. Sequential RV-LV stimulation offers minimal benefit on average and should perhaps be considered only in targeted subsets such as nonresponding patients.

Aged↗
PubMed2004

Temporal repolarization lability differences among genotyped patients with the long QT syndrome.

The investigators sought to test whether certain long QT syndrome (LQTS) mutations are associated with increased repolarization lability and whether repolarization lability (quantified by the QT variability index [QTVI]) is increased in patients with LQTS compared with controls. In 32 genotyped patients with LQTS type 1 (LQT1), 32 genotyped patients with LQTS type 2 (LQT2), and 32 controls, the QTVI was increased in patients with LQT2 (-0.973 +/- 0.394, p = 0.01 vs controls) and in patients with LQT1 with mutations other than KCNQ1-FIN (-0.942 +/- 0.264, p = 0.04 vs controls) but was similar between the KCNQ1-FIN group and controls.

Adult↗
PubMed2004

Modern pacemaker and implantable cardioverter/defibrillator systems can be magnetic resonance imaging safe: in vitro and in vivo assessment of safety and function at 1.5 T.

BACKGROUND: MRI has unparalleled soft-tissue imaging capabilities. The presence of devices such as pacemakers and implantable cardioverter/defibrillators (ICDs), however, is historically considered a contraindication to MRI. These devices are now smaller, with less magnetic material and improved electromagnetic interference protection. Our aim was to determine whether these modern systems can be used in an MR environment. METHODS AND RESULTS: We tested in vitro and in vivo lead heating, device function, force acting on the device, and image distortion at 1.5 T. Clinical MR protocols and in vivo measurements yielded temperature changes <0.5 degrees C. Older (manufactured before 2000) ICDs were damaged by the MR scans. Newer ICD systems and most pacemakers, however, were not. The maximal force acting on newer devices was <100 g. Modern (manufactured after 2000) ICD systems were implanted in dogs (n=18), and after 4 weeks, 3- to 4-hour MR scans were performed (n=15). No device dysfunction occurred. The images were of high quality with distortion dependent on the scan sequence and plane. Pacing threshold and intracardiac electrogram amplitude were unchanged over the 8 weeks, except in 1 animal that, after MRI, had a transient (<12 hours) capture failure. Pathological data of the scanned animals revealed very limited necrosis or fibrosis at the tip of the lead area, which was not different from controls (n=3) not subjected to MRI. CONCLUSIONS: These data suggest that certain modern pacemaker and ICD systems may indeed be MRI safe. This may have major clinical implications for current imaging practices.

Animals↗
PubMed2004

Implantable cardioverter-defibrillators in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy.

OBJECTIVES: The aim of this study was to assess the outcome of arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) patients treated with an implantable cardioverter-defibrillator (ICD). BACKGROUND: Arrhythmogenic right ventricular dysplasia/cardiomyopathy is associated with tachyarrhythmia and an increased risk of sudden death. METHODS: This study included 42 ARVD/C patients with ICDs (52% male, age 6 to 69 years, median 37 years) followed at our center. RESULTS: Mean follow-up was 42 +/- 26 months (range 4 to 135 months). Complications associated with ICD implantation included need for lead repositioning (n = 3) and system infection (n = 2). During follow-up, one patient died of a brain malignancy and one had heart transplantation. Lead replacement was required in six patients as a result of lead fracture and insulation damage (n = 4) or change in thresholds (n = 2). During this period, 33 of 42 (78%) patients received a median of 4 (range 1 to 75) appropriate ICD interventions. The median period between ICD implantation and the first firing was 9 months (range 0.1 to 66 months). The ICD firing storms were observed in five patients. Inappropriate interventions were seen in 10 patients. Predictors of appropriate firing were induction of ventricular tachycardia (VT) during electrophysiologic study (EPS) (84% vs. 44%, p = 0.024), detection of spontaneous VT (70% vs. 15%, p = 0.001), male versus female gender (91% vs. 65%, p = 0.04), and severe right ventricular dilation (39% vs. 0%, p = 0.013). Using multivariate analysis, VT induction during EPS was associated with increased risk for firing in ARVD/C patients; odds ratio 11.2 (95% confidence interval 1.23 to 101.24, p = 0.031). CONCLUSIONS: Patients with ARVD/C have a high arrhythmia rate requiring appropriate ICD interventions. The ICD therapy appears to be well tolerated and important in the management of patients with ARVD/C.

Adolescent↗
PubMed2004

Beat-to-beat heart rate and QT variability in patients with congestive cardiac failure: blunted response to orthostatic challenge.

BACKGROUND: Congestive cardiac failure is associated with increased sympathetic activity and impaired baroreflex function. We sought to test the hypothesis that these patients also have blunted response of beat-to-beat QT interval variability during orthostatic challenge. METHODS: We compared beat-to-beat heart rate and QT interval data in 17 patients with congestive cardiac failure and 17 age-matched normal controls in supine normal breathing, supine controlled breathing, and standing controlled breathing conditions. The ECG data were acquired in lead II configuration at a sampling rate of 1000 Hz. RESULTS: Supine controlled breathing was associated with an increase in spectral HF power (0.15-0.5 Hz) of HR and QT interval time series compared to spontaneous breathing condition only in controls. While there were significant changes in HR, HR LF power, HR LF/HF ratios, and QT variability measures in standing posture in controls, there were no such changes in patients. CONCLUSIONS: This impairment of postural changes of HR variability is most likely due to an impaired baroreceptor function in patients with congestive heart failure. The etiology of this is likely due to an increased cardiac sympathetic and a decreased vagal function. However, the relationship of postural changes in beat-to-beat QT interval variability and baroreflex need further investigation.

Analysis of Variance↗
PubMed2003

Cardiac resynchronization and death from progressive heart failure: a meta-analysis of randomized controlled trials.

CONTEXT: Progressive heart failure is the most common mechanism of death among patients with advanced heart failure. Cardiac resynchronization, a pacemaker-based therapy for heart failure, enhances cardiac performance and quality of life, but its effect on mortality is uncertain. OBJECTIVE: To determine whether cardiac resynchronization reduces mortality from progressive heart failure. DATA SOURCES: MEDLINE (1966-2002), EMBASE (1980-2002), the Cochrane Controlled Trials Register (Second Quarter, 2002), The National Institutes of Health ClinicalTrials.gov database, the US Food and Drug Administration Web site, and reports presented at scientific meetings (1994-2002). Search terms included pacemaker, pacing, heart failure, dual-site, multisite, biventricular, resynchronization, and left ventricular preexcitation. STUDY SELECTION: Eligible studies were randomized controlled trials of cardiac resynchronization for the treatment of chronic symptomatic left ventricular dysfunction. Eligible studies reported death, hospitalization for heart failure, or ventricular arrhythmia as outcomes. Of the 6883 potentially relevant reports initially identified, 11 reports of 4 randomized trials with 1634 total patients were included in the meta-analysis. DATA EXTRACTION: Trial reports were reviewed independently by 2 investigators in an unblinded standardized manner. DATA SYNTHESIS: Follow-up in the included trials ranged from 3 to 6 months. Pooled data from the 4 selected studies showed that cardiac resynchronization reduced death from progressive heart failure by 51% relative to controls (odds ratio [OR], 0.49; 95% confidence interval [CI], 0.25-0.93). Progressive heart failure mortality was 1.7% for cardiac resynchronization patients and 3.5% for controls. Cardiac resynchronization also reduced heart failure hospitalization by 29% (OR, 0.71; 95% CI, 0.53-0.96) and showed a trend toward reducing all-cause mortality (OR, 0.77; 95% CI, 0.51-1.18). Cardiac resynchronization was not associated with a statistically significant effect on non-heart failure mortality (OR, 1.15; 95% CI, 0.65-2.02). Among patients with implantable cardioverter defibrillators, cardiac resynchronization had no clear impact on ventricular tachycardia or ventricular fibrillation (OR, 0.92; 95% CI, 0.67-1.27). CONCLUSIONS: Cardiac resynchronization reduces mortality from progressive heart failure in patients with symptomatic left ventricular dysfunction. This finding suggests that cardiac resynchronization may have a substantial impact on the most common mechanism of death among patients with advanced heart failure. Cardiac resynchronization also reduces heart failure hospitalization and shows a trend toward reducing all-cause mortality.

Cardiac Pacing, Artificial↗
PubMed2003

QT variability.

We hypothesized that temporal lability in ventricular repolarization is a marker for, and is mechanistically related to, increased risk of malignant ventricular arrhythmias. To assess repolarization lability in the surface electrocardiogram, we developed an automated algorithm, based on template matching, to measure beat-to-beat changes in QT interval. We calculate a QT variability index (QTVI) to quantify the relative magnitude of QT interval changes compared to heart rate variability. We found that QTVI is a reproducible measure. It is elevated in patients with ischemic and nonischemic dilated cardiomyopathy compared with age-matched controls (P<.00001). We have also shown that QTVI is elevated in patients with malignant beta-myosin heavy-chain mutations associated with hypertrophic cardiomyopathy. In a study of patients undergoing electrophysiologic testing, QTVI identified patients with cardiac arrest better than electrophysiologic test result and better than other risk stratifiers included in the analysis. QT variability is a marker of electrical disease in the ventricle and may be associated with enhanced risk of life-threatening arrhythmias.

Algorithms↗
PubMed2002

Prognostic value of heart rate variability in chronic congestive heart failure (Veterans Affairs' Survival Trial of Antiarrhythmic Therapy in Congestive Heart Failure).

Although the value of heart rate variability (HRV) for risk stratification after acute myocardial infarction has been demonstrated, the value of low HRV as a predictor of sudden cardiac death in patients with ischemic cardiomyopathy has not been shown convincingly to date. We retrospectively analyzed electrocardiographic data from 179 patients in the Veterans Affairs' Survival Trial of Antiarrhythmic Therapy in Congestive Heart Failure to determine if HRV (expressed as the SD of the normal-to-normal RR intervals [SDNN]) would be useful as a predictor of overall mortality and sudden death. Because our goal was to identify high-risk patients, we compared patients in the lowest quartile of HRV with the remaining patients. Among the 127 patients meeting inclusion criteria, SDNN <65.3 ms (the lowest quartile) was the sole independent factor predictive of survival in a multivariate model (p = 0.0001). A Cox proportional-hazards model revealed that each increase of 10 ms in SDNN conferred a 20% decrease in risk of mortality (p = 0.0001). Furthermore, patients with SDNN <65.3 ms had a significantly increased risk of sudden death (p = 0.016). Thus, HRV was the sole independent predictor of overall mortality and was significantly associated with sudden death in this population.

Aged↗
PubMed2002

Prospective randomized comparison of cooled radiofrequency versus standard radiofrequency energy for ablation of typical atrial flutter.

In patients with atrial flutter, conventional RF ablation may not result in complete isthmus block. This prospective, randomized study tested the hypothesis that the cooled RF ablation is safe and facilitates the achievement of isthmus block with fewer RF applications than with standard ablation for typical atrial flutter. Isthmus ablation was performed in 59 patients (40 men, 64 +/- 14 years) with type I atrial flutter using standard RF (n = 31) or cooled RF (n = 28) catheters with crossover after 12 unsuccessful RF applications. The endpoint was bidirectional isthmus block or a total of 24 unsuccessful RF applications. After the first 12 RF applications, 17 (55%) of 31 standard RF and 22 (79%) of 28 cooled RF patients had bidirectional isthmus block (P < 0.05). After the remaining patients crossed over to the alternate RF ablation system and underwent up to 12 more RF applications, bidirectional isthmus block had been demonstrated in 27 (87%) of 31 standard RF and 25 (89%) of 28 cooled RF patients (P = NS). Isthmus block was not achieved within 24 RF applications in four standard and three cooled RF patients. Mean measured tip temperatures for cooled RF were lower than for standard RF (38.5 degrees C +/- 6.98 degrees C vs 57.2 degrees C +/- 7.42 degrees C, P < 0.0001). Peak temperatures were also lower for cooled RF compared to standard RF (45.7 degrees C +/- 22.7 degrees C vs 63.4 degrees C +/- 9.87 degrees C, P < 0.0001). Importantly, mean power delivered was significantly higher for cooled than for standard RF (42.3 +/- 9.48 vs 34.0 +/- 14.0 W, P < 0.0001). There were no serious complications for either ablation system. During a 12.8 +/- 3.76-month follow-up, there were two atrial flutter recurrences in the cooled RF group and four in the standard RF group (P = NS). In patients with type I atrial flutter, ablation with the cooled RF catheter is as safe as, and facilitates creation of bidirectional isthmus block more rapidly than, standard RF ablation.

Atrial Flutter↗
PubMed2002

Circular mapping catheter entrapment in the mitral valve apparatus: a previously unrecognized complication of focal atrial fibrillation ablation.

Radiofrequency catheter ablation of focal atrial fibrillation triggers within the pulmonary veins is a rapidly developing therapy that relies on both recent technologies and evolving techniques. We describe the entrapment of a circular mapping catheter within the mitral valve apparatus after transseptal catheterization and mapping of the left atrium and pulmonary veins. The occurrence of this previously unreported complication stresses the need for continual monitoring and reporting of adverse effects from new devices and procedures to better inform patients and physicians of the benefits and risks of electrophysiologic interventions.

Atrial Fibrillation↗
PubMed2002

Beat-to-beat QT interval variability associated with acute myocardial ischemia.

Beat-to-beat QT interval variability (QTV) quantifies lability in ventricular repolarization. We hypothesized that myocardial ischemia destabilizes ventricular repolarization and increases QTV. We analyzed 2-hour 2-lead digitized electrocardiogram records of 68 patients in the European ST-T Database. All patients had ischemic episodes during the 2-hour record, annotated by the developers of the database. We determined the normalized QTV (QTVnorm), QT variability index (QTVI), and normalized heart rate variability (HRVnorm) for each 5-minute epoch by automated analysis. QTVnorm was greater during ischemic episodes than during nonischemic episodes (1.41 +/- 0.77 vs. 0.88 +/- 0.23, P <.0001). There was no significant difference in HRVnorm between ischemic and nonischemic episodes (1.22 +/- 0.63 vs. 0.94 +/- 0.18, not significant). The QTVI was higher during ischemic episodes than during nonischemic episodes (0.14 +/- 0.31 vs. -0.051 +/- 0.12, P <.0001). Acute ischemia is associated with labile ventricular repolarization, which manifests as enhanced beat-to-beat QT interval variability. The association between ischemic repolarization liability and arrhythmic risk deserves further study.

Adult↗