Paroxysmal atrioventricular block induced during head-up tilt testing in an apparently healthy man

Utility of Head up Tilt Table Testing to Demonstrate Selective Denervation of the Sinus Node after Cardioneuroablation

A 65-year-old female who underwent cardioneuroablation for recurrent vasovagal syncope presented for 6 month follow-up visit. She had no further syncope after the procedure. A follow up tilt table testing (TT) demonstrated sinus tachycardia and variable degrees of atrioventricular block (AVB) after sublingual glyceryl trinitrate. She had no syncope during the test. As per existing knowledge, the occurrence of AVB during vasovagal reaction induced by TT should be preceded by sinus rhythm slowing.  In this patient, sinus tachycardia during TT demonstrates highly specific denervation of ganglion cells which send postganglionic fibers directly to the sinus node without obvious influence on the atrioventricular node.

A proposal of clinical ECG index "vagal score" for determining the mechanism of paroxysmal atrioventricular block

Background

Paroxysmal atrioventricular block (P-AVB) is a well-known cause of syncope; however, its underlying mechanism is difficult to determine. This study aimed to evaluate a new ECG index, the “vagal score (VS),” to determine the mechanism of P-AVB.

Methods

We evaluated the VS in 20 patients with P-AVB (13 men, 7 women; aged 25–78 years [mean, 59.3 years]). The VS was developed by assigning 1 point each for the following: (1) no AVB or intraventricular conduction disturbance on the baseline ECG, (2) PR prolongation immediately before P-AVB, (3) sinus slowing immediately before P-AVB, (4) initiation of P-AVB by PP prolongation, (5) sinus slowing during ventricular asystole, and (6) resumption of AV conduction with PP shortening, and by assigning –1 point each for (7) the initiation of P-AVB by a premature beat, and (8) resumption of AV conduction by an escape beat. Based on the clinical situations and electrophysiologic findings, we considered the mechanism of P-AVB as vagally mediated or intrinsic conduction disease (ICD).

Results

The VS ranged from 5 to –2 points for each patient. Five patients with a definite vagally mediated P-AVB had high VSs (3–5 points). We observed characteristic ECG findings of ICD consisting of changes in AV conduction by an extrasystole and/or escape beat in only 5 of the 6 patients (83%) with a low VS (1 to –2).

Conclusions

The VS is simple and potentially useful for determining the mechanism of P-AVB. P-AVB with a VS ≥3 strongly suggested a vagally mediated mechanism.

Paroxysmal atrioventricular block: clinical experience with 20 patients

BACKGROUND

Paroxysmal atrioventricular (AV) block is an ill-defined entity, previously described in sporadic cases in association with vasovagal reaction, coronary angiography and distal conduction disease.

METHODS

We describe 20 patients (10 women) aged 26 to 80 years with symptomatic paroxysmal AV block.

RESULTS

Eight patients had ischemic heart disease-three with dilated cardiomyopathy, and two with co-existing carotid sinus hypersensitivity. Eight were taking chronic AV blockers. In five patients, the paroxysmal AV block occurred during a vagal reaction, in one during migranotic headaches, in one following aortic valve replacement and in one while recovering from acute myocardial infarction. The events lasted between 2.2 and 36 s. In 10 patients, the QRS configuration on the electrocardiogram was wide. Immediate treatment consisted of intravenous atropine and fluid supplements in two patients, discontinuation of the AV blocking agents in four, and the insertion of a temporary pacemaker in eight. Seventeen patients required a permanent pacemaker.

CONCLUSIONS

Paroxysmal AV block is an underestimated clinical entity related to vagal reaction, AV blocking drugs and distal conduction disease. Most of our patients eventually required implantation of a permanent pacemaker.

Paroxysmal atrioventricular block in young patients

We describe 17 patients (8 girls, and 9 boys), aged 9.6 +/- 5.7 years, with paroxysmal atrioventricular block (PAVB), a condition rarely described in children. Holter monitoring documented the PAVB in 15 patients, and tilt test was performed in 4 patients (positive in 1). The electrocardiograph (ECG) was normal in 7 patients. Two patients had acquired and 11 patients had congenital heart disease (CHD). Syncope or presyncope were present in 7 patients. A normal ECG was significantly more frequent in symptomatic patients. Pauses were significantly longer in girls and in children <5 years. PAVB was recorded only during nocturnal hours in 6 patients and throughout the day in the others. The sinus rate decreased during PAVB in 6 patients and increased in 4 (generally younger girls with symptoms). Permanent pacemakers were implanted in 13 patients, including 7 asymptomatic patients with CHD and severe bradycardia. During follow-up (3.7 +/- 2.5 years), 1 patient developed complete AVB. Although PAVB was still present in 91% of paced patients, symptoms did not recur because pacing prevented the pauses. In conclusion, PAVB is a rare arrhythmia. Autonomic nervous system dysfunction seems to play an etiological role and permanent pacing was an effective treatment.

Mechanisms and clinical significance of transient atrioventricular block during dobutamine stress echocardiography

OBJECTIVES

The purpose of this study was to investigate the possible mechanism and the clinical significance of transient atrioventricular block (AVB) during dobutamine stress echocardiography (DSE).

BACKGROUND

Transient AVB occurs rarely during DSE; however, the mechanisms responsible for blocks are unclear.

METHODS

A retrospective analysis of clinical, echocardiographic, catheterization, revascularization and head-up tilting test data was conducted in patients who developed transient AVB during DSE.

RESULTS

A total of 302 patients with known or suspected coronary artery disease (CAD) underwent DSE before coronary angiography between November 1997 and August 1998. Transient AVB developed in 12 patients during the test. Mobitz I block was noted in six patients and Mobitz II block in the other six patients. Nine of these 12 patients were subsequently shown to have CAD and three had no significant coronary artery stenosis. Mobitz II block was observed only in patients with CAD, while Mobitz I block occurred in three patients with and three patients without CAD (p < 0.05). Eight of the nine patients with CAD underwent a successful coronary angioplasty with or without stenting and a repeat DSE revealed no recurrence of heart block except in one patient. Head-up tilting test in the 12 patients revealed a positive response in three of the nine patients with and all three patients without CAD. A negative head-up tilting test was likely to be observed in patients with, as compared with those without, CAD in this study population (p < 0.05).

CONCLUSIONS

Transient AVB is not an infrequent manifestation during DSE. Both myocardial ischemia and neurally mediated vagal reflex may be responsible for this phenomenon. The development of Mobitz II block during DSE is indicative of the presence of CAD. A successful revascularization in patients with CAD who develop transient AVB may abolish this phenomenon.

Treatment of advanced atrioventricular block with beta-adrenergic blockade therapy

A 26-year old woman, who experienced syncope associated with advanced AV block, was referred for further evaluation. Electrophysiological study showed normal SA and AV node physiology. Syncope associated with advanced AV block on the electrocardiogram was induced by head-up tilt test. Oral propranolol therapy completely prevented the AV block and syncope induced by head-up tilt. The physician should be aware of advanced AV block associated with neurocardiogenic syncope, especially before permanent - pacemaker therapy is considered. The head-up tilt test is a useful diagnostic tool for an etiology of paroxysmal AV block.