Atrial fibrillation in patients with Wolff-Parkinson-White syndrome.
Explore the source record for details and available documents.
Atrial Fibrillation↗
Biomedical subjects
Raymond Yee
Publications and source records attributed to Raymond Yee.
Beta blockers normalize QT hysteresis in long QT syndrome.
OBJECTIVES: This study was performed to evaluate the impact of beta blockers on QT adaptation to heart rate during the exercise and recovery phases of exercise testing in long QT syndrome. BACKGROUND: Long QT syndrome is characterized by familial syncope and sudden death in the context of sudden heart rate changes. QT hysteresis has been proposed as a phenotypic marker of long QT syndrome, suggesting altered QT adaptation to changes in heart rate. METHODS: Fourteen patients with long QT syndrome (aged 26 +/- 16 years, 6 male) and 10 healthy volunteers (aged 37 +/- 11 years, 9 male) underwent graded exercise testing with continuous lead II electrocardiographic monitoring. Long QT patients underwent repeat assessment after 1 month of beta blockade. QT intervals at matching heart rates were compared during exercise and recovery to determine the effect of beta blockade on QT hysteresis, defined as the recovery QT peak interval subtracted from the exercise QT peak interval. RESULTS: In the 14 long QT syndrome patients, beta blockers slowed the resting heart rate without affecting the corrected QT interval (502 +/- 52 ms baseline vs 481 +/- 40 ms beta blocker, P =.17). The increase in heart rate with exercise was similar in the 3 groups (P =.73). Exaggerated hysteresis of the QT interval was seen in the patients with long QT syndrome at baseline compared with controls (46 +/-19 ms vs 19 +/- 11 ms 1 minute into recovery, P =.006). Beta blockers had minimal effect on the QT interval but markedly reduced hysteresis with minimal separation of the exercise and recovery QT/RR curves (25 +/- 35 ms 1 minute into recovery, P =.027). The combined curve separation at all 6 time points analyzed was 165 +/- 95 ms in patients with long QT syndrome at baseline, 40 +/- 131 ms after beta blockade, and 29 +/- 30 ms in control subjects (P =.002). Comparison of the beta blocker effect on hysteresis in the 2 genotypes suggested a greater reduction in hysteresis in the 3 patients with long QT syndrome 1 compared with the 11 patients with long QT syndrome 2. CONCLUSIONS: Beta blockers reduce QT hysteresis in patients with long QT syndrome to values seen in normal patients. This improved QT adaptation to changes in heart rate may explain the clinical benefit of beta blockers in long QT syndrome.
Adolescent↗
Sex differences in QTc interval and QT dispersion: dynamics during exercise and recovery in healthy subjects.
BACKGROUND: Sex differences have been described in resting cardiac repolarization and susceptibility to torsade de pointes in humans. This study compares the QT-interval and QT-dispersion dynamics during exercise and recovery between healthy men and women. METHODS: Twenty healthy subjects (10 males aged 30 +/- 4 years, 10 females aged 31 +/- 11 years) underwent symptom-limited bicycle ergometry followed by a 10-minute recovery period. Digital 12-lead electrocardiograms (ECG) were recorded every 10 seconds during exercise and recovery. For each lead, the QTp interval (Q onset to T peak) was automatically measured by use of QT Guard (GE Marquette, Milwaukee, Wis). QTp dispersion was defined as the difference between the maximum and minimum QTp for each ECG. To quantify QT dynamics, we fit the QTp in lead V(3) (QTpV(3)) versus cycle length (CL) relationship to a quadratic function during exercise and recovery with nonlinear regression analysis. Similar regression analysis was performed for the QTp dispersion versus CL relationship. RESULTS: At baseline, QTpcV(3) was longer in women than in men (338 +/- 25 vs 278 +/- 15 ms, P <.0001), but QTp dispersion was similar (35 +/- 18 vs 41 +/- 19 ms). At peak exercise, QT dispersion decreased compared with baseline in both men and women. During exercise and recovery, women had a steeper QTpV(3)-CL relationship. QTpV(3) hysteresis, a measure of the exercise and recovery QTpV(3)-CL curve separation, was greater in women than in men when measured 1 minute into recovery (33 +/- 20 vs 6 +/- 8 ms, P <.001). No sex difference in QTp-dispersion-rate adaptation was observed during exercise or recovery. CONCLUSIONS: Healthy women exhibit greater QT-interval-rate adaptation during both exercise and recovery than men, resulting in more QT-interval hysteresis. Greater QT prolongation during decelerating heart rates in recovery may play a role in increasing proarrhythmia risk in women.
Adult↗
Biventricular pacing improves quality of life and exercise tolerance in patients with heart failure and intraventricular conduction delay.
BACKGROUND: Biventricular pacing improves left ventricular dysynchrony, leading to improvement in congestive heart failure symptoms. The extent of placebo effect, the predictors of response and the long term benefits are unknown. PATIENTS AND METHODS: Forty-five patients with symptomatic congestive heart failure underwent implantation of a biventricular pacing system over a 30-month period (age 65 10 years, 37 men). Patients underwent implantation of a biventricular pacemaker or implantable defibrillator one month or longer after stabilization of congestive heart failure on maximal medical therapy, including angiotensin-converting enzyme inhibitors in 84% of patients and beta-blockers in 56% of patients. Three patients had New York Heart Association (NYHA) class II heart failure, 34 had NYHA class III and eight had NYHA class IV. Cardiomyopathy was ischemic in 31 patients, dilated in 12 and the result of other causes in two. The left ventricular ejection fraction was 19 5%. RESULTS: Implantation of the biventricular pacing system was successful in 38 of 45 patients (84%). Two patients had successful implantation with a second attempt, and one patient had an epicardial lead implant. Lead dislodgement occurred in four patients, with successful repositioning in all. During a mean follow-up of 10 7 months, the Minnesota Living with Heart Failure Questionnaire quality of life index score improved from 62 16 to 42 22 at one month (P<0.001), but subsequently returned to intermediate levels (55 26 at three months, 48 26 at six months and 56 34 at one year, P=0.50). In seven patients with deferred device activation, quality of life scores also improved by 10 15 points from baseline to one month with VDI 35 pacing, and improved a further 15 20 points with left ventricular lead activation. The mean NYHA class fell from 3.1 0.5 at baseline to 2.7 0.7 at one month (P=0.006) and remained stable thereafter (2.8 0.9 at three months, 2.8 0.9 at six months). Six patients died during follow-up, one patient had a cardiac transplantation and subsequently died, one patient had a successful cardiac transplantation and one patient underwent insertion of a left ventricular assist device. Death occurred due to progressive heart failure in five patients, sudden death occurred in one patient and a noncardiovascular cause resulted in the death of one patient. An analysis of NYHA responders (NYHA class improvement of 1 or more at last follow-up, 44% of patients) and quality of life responders (score improvement of 10 or more at last follow-up, 57% patients) did not show any difference in age, sex, heart failure etiology, QRS width, ejection fraction or baseline NYHA class. CONCLUSIONS: Biventricular pacing improves quality of life and NYHA class in patients with advanced heart failure and intraventricular conduction delay. The attenuated benefit seen over time may be related to initial placebo effect or simple dual- chamber pacing, or the natural history of the underlying disease. Identification of patients most likely to respond to biventricular pacing was not possible.
Aged↗