Alok Maheshwari

Adenosine Induced Ventricular Fibrillation in Wolff‐Parkinson‐White Syndrome

GUPTA, A. K., et al.: Adenosine Induced Ventricular Fibrillation in Wolff‐Parkinson‐White Syndrome. VF was observed in four patients (group A) with preexcited AF presenting to the emergency department who had been given 12 mg of adenosine. These patients were resuscitated and underwent electrophysiological study and catheter ablation of the accessory pathway (AP). In a control (group B) of five patients with manifest AP, sustained AF was induced by rapid atrial pacing during electrophysiological study and 12 mg of adenosine was administered. The ECG and electrophysiologic features in the two groups were compared. All patients had a single manifest AP. In group A, three patients had a left free‐wall AP and one patient had a posteroseptal AP, while in the control group all had left free‐wall APs. The antegrade AP effective refractory period (ERP) in groups A and B was 227 ± 29 and 289 ± 37 ms, respectively (P < 0.05). The atrial ERP was 210 ± 17 versus 219 ± 21 ms, respectively, in groups A and B (P > 0.05). The shortest R‐R interval during AF in group A was 246 ± 51 ms and 301 ± 60 ms in group B (P value < 0.05). After adenosine, no patient in group B developed VF. Adenosine may cause VF when administered during preexcited AF. This phenomenon is seen in patients having APs with short refractory periods.

A Novel Catheter Design for Laser Photocoagulation of the Myocardium to Ablate Ventricular Tachycardia

AbstractNd:YAG laser energy has been proposed as an alternative to radiofrequency energy for ablation of ventricular tachycardia (VT) associated with coronary artery disease (CAD) in an effort to increase lesion size and success rates. However, issues of catheter design to maintain flexibility and ensure adequate tissue contact have hindered development of laser catheters.We developed and tested a prototype 8 Fr. steerable catheter with a flexible and extendible tip (designed to ensure tissue contact and efficient ventricular mapping), which projects the laser beam through a side port containing a lens-tipped optical fiber that rests against the endocardial surface. The catheter has a channel for simultaneous saline irrigation to displace the interceding blood and discharge a laser beam between two electrodes for bipolar mapping and a thermocouple for temperature monitoring. The catheter was tested on bench top using the epicardial surface of freshly slaughtered bovine hearts and in vivo using six anaesthetized closed-chest sheep. In vitro experiments demonstrated that lesion size increased linearly with applied power up to 40 watts. When compared to radio frequency, laser energy penetrated more deeply into the myocardium. In the in vivo studies, using increasing powers of up to 40 watts for application times of 60 to 120 seconds created circular or elliptical lesions with surface dimensions up to 12 mm × 12 mm and depth of 9 mm (full LV wall thickness with a mean lesion diameter of 9.9 ± 5.2 mm and depth 5.8 ± 3.2 mm). Most lesions, 16 total in both right and left ventricular walls were transmural or near transmural in thickness. Lesions demonstrated coagulation necrosis with smooth well-demarcated borders. No animal suffered cardiac perforation, hypotension, hemopericardium, damage to cardiac valves, or cavitation effect from any of the ablations. Runs of VT were seen during energy application at the highest laser outputs in two animals.In conclusion, this catheter design provides effective endocardial delivery of laser energy and is capable of creating transmural or nearly transmural lesions in vivo and in vitro, thereby potentially increasing the efficiency of VT ablation in CAD patients.

Primary Radiofrequency Ablation for Incessant Idiopathic Ventricular Tachycardia

GUPTA, A.K., et al.: Primary Radiofrequency Ablation for Incessant Idiopathic Ventricular Tachycardia. Fascicular VT and RVOT tachycardia are sometimes difficult to induce by programmed electrical stimulation (PES), despite pharmacologic provocation. In such instances, catheter mapping is hampered and efficacy of catheter ablation is difficult to judge. The study included nine patients who presented with incessant idiopathic VT and were directly taken to the electrophysiological laboratory for RF ablation. During the same period, elective ablation was performed on 108 patients with idiopathic VT. The success rate, procedural and fluoroscopy times number of energies, and the peak temperature were evaluated and compared. Of the nine patients, seven had incessant fascicular VT and two had RVOT tachycardia. The mean VT cycle length was 356 ± 32 ms and the earliest endocardial activation time during VT was 23.6 ± 6 ms relative to surface QRS complexes. A fascicular potential was not seen in three of the seven patients with fascicular VT. The mean procedural time was 71 ± 32 minutes and 144 ± 40 minutes (P = 0.023) while the fluoroscopy time was 14.6 ± 4.6 minutes and 30 ± 16 minutes (P < 0.001), respectively, in the primary ablation and elective groups. The total number of RF energies delivered was 2.0 ± 1.3 versus 7.4 ± 5.6 (P = 0.07), respectively. The significantly increased procedural time during elective ablation was largely due to time spent in fascicular VT induction. All patients in the primary ablation group were successfully ablated and none had a recurrence. Primary ablation is a safe and effective option in patients with incessant idiopathic VT. Moreover, in fascicular VT, it is superior to elective ablation in terms of success, fluoroscopy and procedural times.

Implantable cardioverter defibrillator therapy in patients with ischemic or non-ischemic cardiomyopathy and nonsustained ventricular tachycardia

AbstractBackground: Mortality benefit from implantable cardioverter defibrillator (ICD) therapy in ischemic cardiomyopathy (ICM) with non-sustained ventricular tachycardia (NS-VT) and inducible VT is well defined. Although NS-VT may suggest an increased risk of sudden cardiac death (SCD) in non-ischemic cardiomyopathy (NICM), the role of ICD therapy is unclear. This retrospective study compares follow-up data in these two groups after ICD implantation. Methods: 153 consecutive patients with ICD implantation for NS-VT were analyzed. ICM patients received an ICD if they had inducible VT at electrophysiology study (EPS). NICM patients did not routinely undergo EPS before ICD implantation. Results: There were 48 patients (33 males) in NICM group and 105 patients (89 males) in the ICM group. Baseline characteristics including mean ejection fraction (EF), distribution in various New York Heart Association (NYHA) classes, and the mean duration of follow up in the two groups were similar. 50% of the patients in the NICM group and 36% in the ICM group received appropriate therapies (p = 0.106). The mean number of appropriate therapies in the two groups were similar (23.3 ± 56.7 and 22.5 ± 59.5 respectively, p = NS). The percentage of patients with inappropriate therapies in the two groups were 27% and 23% respectively (p = NS). Patients in the NICM group received appropriate ICD discharges at a greater rate (p = 0.02). Conclusion: Patients undergoing ICD implantation for NICM and NS-VT receive appropriate ICD therapy at a greater rate than those implanted for ICM, NS-VT, and a positive EPS. Although these data do not prove survival benefit in NICM, they suggest a beneficial effect.

Can Cardiac Pacing Prevent Neurocardiogenic Syncope

Neurocardiogenic syncope (NCS) is a common disorder, generally with a benign prognosis. However, in a subgroup of patients with this disorder, profound bradycardia or asystole accompanies the syncopal episodes. Asystole during these syncopal episodes may mimic sudden cardiac death and has been termed ‘‘malignant’’ vaso-vagal syndrome because of the associated significant morbidity [1]. Rarely, deaths have been reported. The precise pathophysiology and prognosis of this syndrome is not yet fully understood. Occasionally, these episodes are not preceded by any significant prodromal warning symptoms. Treatment of recurrent NCS has centered primarily on the use of pharmacological interventions: b blockers, disopyramide, certain vasoconstrictor agents and serotonin reuptake inhibitors (fluoxetine hydrochloride) have been of particular interest. Volume expanders, such as fludrocortisone acetate, salt tablets and belladona alkaloids such as scopolamine are still in use. Since hypotension in patients with NCS is frequently accompanied by bradycardia, implantation of a permanent pacemaker has also been investigated. However, the role of cardiac pacing for treatment of recurrent NCS remains somewhat controversial.