Congestive Heart Failure and VVI Pacing Mode: Dynamic Behavior of the Dispersion of Ventricular Repolarization

Dynamic Behavior of the Dispersion of Ventricular Repolarization. The aim of this study was to evaluate the circadian variation in the spatial dispersion of ventricular repolarization in continuously paced patients with congestive heart failure (CHF). Fourteen patients (10 males, 4 females, aged 65 ± 5 years) with CHF due to dilated cardiomyopathy (DCM) and an echocardiographic ejection fraction of 28%± 3% were studied. All patients underwent AV functional RF ablation and permanent pacemaker implantation for drug refractory chronic atrial fibrillation (AF). Patients were evaluated at 1 month postimplant with a three-channel 24-hour Holter monitor, using the three plane Frank orthogonal leads (X, Y, and Z), in VVI pacing mode at 70 beats/min. For each hour, the mean value of spike-T interval dispersion of the first five beats was measured. The control group consisted of 20 patients without structural heart disease, but with AF and complete AV block, continuously paced in WI mode at 70 beats/min. The dispersion of the spike-T interval had a circadian behavior in the study population, with higher values at night and lower during the daytime. During the daytime, the mean value of spike-T interval dispersion was 39 ± 5 ms and during the nighttime it was 45 ± 7 ms (P = 0.003). Such a difference between day and night was not found in the control group (38 ± 6 ms and 40 ± 8 ms, respectively, P = NS), In the daytime period the mean value of spike-T interval dispersion of our study population was comparable to that of the control group (P = NS), while during the nighttime it was significantly higher (P = 0.0004). In conclusion, by evaluating the dispersion of ventricular repolarization in two dimensions, space and time, a circadian variation was found in paced patients with CHF due to DCM. The increased QT dispersion in these patients during the nighttime period was attributed to different effects of vagal activity in normal and abnormal myocardial areas.     

Successful Withdrawal from the Right Coronary Artery of an NIR Stent Dislodged from the Balloon Catheter

A 58-year-old patient who underwent right coronary arterial angioplasty with NIR stent placement is described. The stent was dislodged from the balloon catheter and a technique of stent entrapment with two guidewires was successfully performed to remove it from the coronary artery.     

Heart Rate‐Dependence of QTc Intervals Assessed by Different Correction Methods in Patients with Normal or Prolonged Repolarization

Background: There is a continuing debate about the optimal method for QT interval adjustment to heart rate changes. We evaluated the heart rate dependence of QTc intervals derived from five different QT correction methods. Methods: Study patients (n = 123, age 68 ± 11 years) were dual‐chamber device recipients with baseline normal or prolonged QT interval who had preserved intrinsic ventricular activation with narrow QRS complexes. Patients were classified to either Normal‐QT (n = 69) or Prolonged‐QT (n = 54) groups. Serial QT intervals were recorded at baseline (52 ± 3 beats per minute) and following atrial pacing stages at 60, 80, and 100 beats per minute. The QTc formulae of Bazett, Fridericia, Sagie‐Framingham, Hodges, and Karjalainen‐Nomogram were applied to assess the effect of heart rate on the derived QTc values by using linear mixed‐effects models. Results: Heart rate had a significant effect on QTc regardless of the formula used (P < 0.05 for all formulae). The Bazett's formula demonstrated the highest QTc variability across heart rate stages (highest F values) in both patient groups (in the total cohort, F = 175.9). In the following rank order, the formulae Hodges, Karjalainen‐Nomogram, Sagie‐Framingham, and Fridericia showed similar QTc heart rate dependence at both slower and faster heart rates in both patient groups (F = 21.8, 25.6, 28.8, 36.9, in the total cohort, respectively). Conclusions: Of the studied QTc formulae, the Bazett appeared the most heart rate dependent. Our results suggest the use of Hodges and the Karjalainen‐Nomogram secondly to ensure least heart rate dependence of QTc intervals in patients with either normal or prolonged repolarization. (PACE 2010; 553–560)     

DAU 6215, a novel 5-HT3-receptor antagonist,selectively antagonizes scopolamine-induced deficit in a passive-avoidance task,but not scopolamine-induced hypermotility in rats

Abstract— This study examined the effects of DAU 6215, a selective 5-HT₃-receptor antagonist, on either impairment of a passive-avoidance task or hypermotility, both caused by scopolamine in rats. In the first experiment, scopolamine (0·75 mg kg^?1, i.p.) disrupted acquisition of a one-trial ‘step through’ passive-avoidance response. Pretreatment with DAU 6215 (1, 10, 30 and 100 μg kg^?1, i.p.) antagonized this deficit induced by scopolamine, with a bell-shaped dose-response curve. Scopolamine (0·75 mg kg^?1, i.p.) produced a significant increase in locomotor activity which was unaffected by pretreatment with DAU 6215 (10 and 30 μg kg^?1, i.p.). The present results further support the suggestion that 5-HT₃-receptor antagonists may prevent the memory disturbance caused by a reduction in central cholinergic function in the rat. The inefficacy shown by DAU 6215 on hyperactivity induced by scopolamine appears to rule out the possibility of a pharmacokinetic interference between DAU 6215 and scopolamine.