Ablation for atrioventricular nodal reentrant tachycardia with a prolonged PR interval during sinus rhythm: the risk of delayed higher-degree atrioventricular block.

INTRODUCTION: Delayed higher-degree atrioventricular (AV) block can develop after slow pathway ablation for AV nodal reentrant tachycardia with a preexisting first-degree AV block. Retrograde fast pathway ablation is considered as an alternative approach for patients with a markedly prolonged PR interval and no demonstrable anterograde fast pathway function at baseline. This study aimed to determine the long-term reliability of AV conduction after retrograde fast pathway ablation in comparison to slow pathway ablation in patients with AV nodal reentrant tachycardia and a first-degree AV block at baseline. METHODS AND RESULTS: Among 43 patients with AV nodal reentrant tachycardia and a prolonged PR interval (defined as >or=200 msec), 10 patients without demonstrable dual pathway physiology underwent ablation of the retrograde fast pathway, and 33 patients with dual pathway physiology underwent slow pathway ablation. Persisting intraprocedural second- or third-degree AV block requiring pacemaker implantation occurred in one patient (10%) after retrograde fast pathway ablation and in one patient (3%) after slow pathway ablation. During the long-term follow-up of 61 +/- 39 months after retrograde fast pathway ablation, no delayed second- or third-degree AV block occurred, and the PR interval remained unchanged (308 +/- 60 msec vs 304 +/- 52 msec). During the follow-up of 37 +/- 25 months after slow pathway ablation, a delayed complete heart block developed in two patients, and a second-degree AV block developed in two patients. Three patients aged 66, 75, and 76 years died suddenly of unknown cause 4, 16, and 48 months following slow pathway ablation, respectively. CONCLUSIONS: Slow pathway ablation was associated with a significant risk of a delayed higher-degree AV block in patients with AV nodal reentrant tachycardia and a prolonged PR interval at baseline. Retrograde fast pathway ablation for patients with a first-degree AV block and no demonstrable dual pathway physiology was associated with a higher intraprocedural risk of complete AV block but did not result in the development of higher-degree AV block during the long-term follow-up of up to 9 years.

Acute stent thrombosis in a sirolimus eluting stent after wasp sting causing acute myocardial infarction: a case report.

INTRODUCTION: Hymenoptera venoms contain thrombogenic substances that might be responsible for cardiovascular events independent of anaphylactic reactions. CASE PRESENTATION: We report a 55-year-old man who experienced an acute ST-elevation myocardial infarction after wasp sting. The patient presented without signs of anaphylaxis or shock. The coronary angiography showed an acute stent thrombosis of the right coronary artery. Percutanous coronary intervention was performed immediately and this is an example for a cardiovascular complication associated with a hymenoptera sting, since the vasoactive, inflammatory, and thrombogenic substances of hymenoptera venoms potentially cause stent thrombosis and myocardial ischemia. To the best of our knowledge this is the first report of acute stent thrombosis in a sirolimus-eluting stent following hymenoptera sting. CONCLUSION: Stent thrombosis is a possible complication after wasp sting induced by thrombogenic substances of the hymenoptera venom.

Reinitiation of ventricular macroreentry within the His-Purkinje system by back-up ventricular pacing - a mechanism of ventricular tachycardia storm.

BACKGROUND: We describe immediate reinitiation of macroreentry ventricular tachycardia (VT) involving the His-Purkinje system by ventricular pacing from the electrode of an implantable cardioverter defibrillator (ICD) as a mechanism of VT storm refractory to ICD therapy. METHODS AND RESULTS: Repetitive reinitiation of bundle branch reentry tachycardia (BBRT), interfascicular tachycardia, or both VTs by ventricular pacing was identified in four ICD patients presenting with VT storm or incessant VT. All patients had a pre-existing prolonged HV interval (75 +/- 9 ms) and left bundle branch block (LBBB) or bifascicular block during sinus rhythm. The VTs included BBRT with LBBB in three patients and interfascicular tachycardia with right bundle branch block (RBBB) and left anterior or left posterior fascicular block in two patients. The paced beats from the ICD electrode exhibited a LBBB pattern of depolarization in two patients and a RBBB contour in V1 and V2 with left axis deviation in two patients. The QRS complex during pacing from the ICD electrode closely resembled that of the recurrent VT in all four patients suggesting that the pacing site of the ICD electrode was in proximity to the myocardial exit site of the bundle fascicle used for antegrade conduction during the reinitiated VT. Ventricular pacing from the ICD electrode after termination of the VT apparently encountered the retrograde refractoriness of this bundle fascicle and allowed immediate re-propagation of the wavefront orthodromically along the VT circuit. BBRT was eliminated by ablation of the right bundle branch. Successful ablation of the interfascicular tachycardias was achieved by targeting (1) an abnormal potential of the distal left posterior Purkinje network or (2) a diastolic potential during VT in the midinferior left ventricular (LV) septum. CONCLUSIONS: Repetitive reinitiation of BBRT and interfascicular tachycardia by ventricular pacing from the ICD electrode should be considered as a mechanism of VT storm refractory to ICD therapy in patients with a pre-existing conduction delay within the His-Purkinje system.