Relation Between Cycle Length, Volume, and Pressure in Type I Atrial Flutter

Assuming that type I atrial flutter is a macroreentrant circuit, its cycle length should vary with the atrial dimensions. In order to test this hypothesis, flutter cycle length was measured while inducing atrial volume and pressure changes by postural and pharmacological means in seven patients undergoing a therapeutic programmed stimulation for type 1 atrial flutter conversion. Right atrial volume was estimated from B-mode echocardiography data. Basal values were compared with those obtained during inspiration, expiration, Valsalva maneuver, negative tilt (head down), and positive tilt (head up) with 0.8–1.6 mg p.o. nitroglycerin. The right atrial size increased slightly from 17.8 to 18.3 cm² (P = 0.04) during the pressure load induced by negative tilt (+ 3 mmHg), with a corresponding lengthening of the flutter cycle length from 228 to 233 msec (P = 0.02). Similarly, pressure unloading of -2 mmHg by positive tilting and nitrates was accompanied by a decrease in right atrial size to 16.6 cm² (P = 0.04), with a corresponding decrease in cycle length from 228 to 219 msec (P = 0.03). Respiratory maneuver yielded similar results with an inspiratory cycle lengthening, expiratory shortening, and further shortening during Valsalva maneuver. These experiments demonstrate a direct relation between cycle length and atrial volume in human type I atrial flutter. They underline the importance of the right heart preload and atrial size for the electrophysiological characteristics of type I atrial flutter. Beside its fundamental interest, this finding is important for the understanding of the mechanism of maintenance and therapeutic responses of this common arrhythmia.     

Undersensing of VF in a Patient With Optimal R Wave Sensing During Sinus Rhythm

We describe a case of potentially fatal undersensing of VF by a third generation ICD with predetermined automatic gain control. In this patient, ventricular sensing was optimal, as R wave amplitudes during sinus rhythm were at least 16 mV. Cyclical, high amplitude signals during VF elevated the sensing floor to such an extent that complete undersensing of subsequent lower amplitude local electrograms occurred. This led to bradypacing and complete ICD therapy failure. Therefore, high R wave amplitudes during sinus rhythm do not warrant flawless sensing during VF. (PACE 2004; 27[Pt. I] 833–834)     

Catheter Ablation for Recurrent Tachyarrhythmias. Clinical Experience with Two Different Techniques of Ablation in 21 Patients

Between 1984 and 1988, 21 patients underwent catheter ablation for drug refractory arrhythmias. Nine patients presented atrial flutter, atrial fibrillation or atrial tachycardia, nine had supraventricular tachycardia (one AV nodal reentrant tachycardia, one reciprocating tachycardia due to concealed accessory pathway and seven XMPW syndrome). Three had ventricular tachycardia. Fourteen patients were treated with direct current shock ablation (DC) and seven patients with radiofrequency ablation (RF). Eight patients underwent ablation of the His bundle. In six patients permanent AV block could be induced and in two first-degree AV block. All became asymptomatic (two with additional antiarrhythmic drug therapy). In four patients with WPW syndrome DC ablation of the accessory pathway was attempted. In one patient a permanent block in the accessory pathway and in another an intermittent block were obtained. In the two remaining patients with accessory pathways the ablation failed to interrupt the retrograde conduction in one the retrograde conduction was modified: however, in the other no change could be demonstrated. Two patients underwent ventricular foci ablation, with one partial success (arrhythmia controlled with associated drug therapy) and one failure. Three patients had RF His bundle ablation (two for atrial flutter and one for atrial fibrillation). One complete atrioventricular block, one first degree AV block and one first degree AV block associated with right bundle branch block were induced. Recurrence of tachyarrhythmias was prevented only in the patient with complete atrioventricular block. RF ablation of accessory pathway was performed in three patients. It resulted in anterograde block in the accessory pathway in the first patient; a slight modification of the retrograde refractory period in the second and no change was noted in the last one. The first of these three patients could then be controlled with drug therapy. The other two patients underwent surgical dissection of the pathway. One patient underwent an unsuccessful attempt of ventricular focus ablation with RF energy. Complications were more common with DC than with RF ablation but serious ventricular arrhythmias were also observed during RF ablation. Thus, DC ablation was completely successful in eight of 14 patients (57%), partially successful with the addition of drug therapy in three patients (21%) and failed in 22%. HF ablation was successful in only one patient (14.5%) and partially successful in another one (14.5%). This relatively low success rate is due in part to the design of the device and the electrodes used in this study. With technical improvements of RF ablation it seems reasonable to expect that this method will play a significant role in the management of drug refractory arrhythmias, since RF ablation, when compared to DC ablation, has the major advantage not to require general anesthesia during the procedure.     

Dual Chamber Pacing in Hypertrophic Obstructive Cardiomyopathy: Beneficial Effect of Atrioventricular Junction Ablation for Optimal Left Ventricular Capture and Filling

Clinical improvement with dual chamber pacing bas largely been reported in patients suffering from hypertrophic obstructive cardiomyopathy and mainly attributed to the reduction of the subaortic pressure gradient. To be effective, pacing must induce a permanent and complete capture of the LV. In two patients of our collective, symptoms (angina and dyspnea NYHA Class III and/or syncopes) persisted or relapsed despite pacing. This was related to the inability to obtain full LV capture due to a too-short native PR interval. RF ablation of the AV junction was therefore performed in botb patients, resulting in permanent AV block in one and prolonged PR interval up to 310 ms in the second. Pacing was thereafter associated with an immediate and significant clinical improvement related to permanent LV capture, whatever the patient's activity. After RF ablation, the AV delay was set up to induce the best LV filling, as assessed by Doppler analysis of mitral flow. Our observations suggest that RF ablation or modification of the AV junction can be a successful procedure in some patients with residual or recurrent symptoms, when the latter result from a loss of capture or from the inability to program an AV delay tbat does not compromise the active component to LV filling. Doppler echocardiography is a simple and effective mean to assess the hemodynamic effect of AV interval modulation in this setting.     

Atrial Septal Defect Measurement with a Guidewire Loop

A practical, simple and cheap technique using a guidewire loop for transvenous measurement of the size of a patent foramen ovate is presented. We applied this device in four patients without complication. To clear a suspected cause of paradoxical embolism was the indication of this procedure. Sizes between 16 and 4 mm were documented. We conclude that this technique may be of value in determining criteria for surgical closure or for the evaluation of transcatheter obliteration in hemodynamically nonrelevant atrial septal defects.     

Bezold-Jarisch-Like Phenomenon Induced by Radiofrequency Ablation of a Left Posteroseptal Accessory Pathway via the Coronary Sinus

RF Ablation-Induced Bezold-Jarisch Phenomenon. We report a case of asystole induced by radiofrequency (RF) ablation via the coronary sinus in a 35-year-old man suffering from symptomatic left posteroseptal accessory pathway. RF application provoked progressive slowing of the sinus rhythm, disappearance of the preexcitation, and an 8-second period of asystole followed by atrial fibrillation. The causal mechanism proposed is a strong stimulation of va-gal afferent pathways linked with sensory endings of the inferoposterior myocardial wall leading to a Bezold-Jarisch-like phenomenon.