Junctional escape rhythm

If the sinoatrial node fails to generate an impulse, the AV junction may take over and initiate an escape beat, as mentioned earlier. These escape beats are the hearts back up system to keep the heart functioning (Fig. 6.25). 

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A-V junctional escape rhythms, junctional tachycardia atrial rhythms with slowed A-V conduction or A-V block... 

A 9-year-old boy whose serum lithium concentration was 1.29 mmol/1 had a sinus bradycardia with a junctional escape rhythm (40 beats/minute), which normalized at a lower lithium concentration (130). 

A comparison between procainamide and propafenone in 62 patients, who had undergone coronary artery bypass grafting or valvular surgery within 3 weeks and developed sustained atrial fibrillation, showed that both drugs converted the dysrhythmia to sinus rhythm in up to 76% of cases, but that propafenone did it more quickly (3). Symptomatic arterial hypotension occurred more frequently with procainamide (nine of 33 patients) than with propafenone (two of 29 patients). Other adverse effects of procainamide were nausea (n = 2) and junctional escape rhythm (n = 2). 

First degree, second degree (Mobitz type I), third degree AV junctional escape rhythms, junctional tachycardia Atrial arrhythmias with slowed AV conduction or AV block Particularly paroxysmal atrial tachycardia with AV block Sinus bradycardia... 

B. With chronic intoxication, visual disturbances, weakness, sinus bradycardia, atrial fibrillation with slowed ventricular response rate or junctional escape rhythm, and ventricular arrhythmias (ventricular bigeminy or trigeminy, ventricular tachycardia, bidirectional tachycardia, and ventricular fibrillation) are common. Accelerated junctional tachycardia and paroxysmal atrial tachycardia with block are frequently seen. Hypokalemia and hypomagnesemia from chronic diuretic use may be evident and appear to worsen the tachyarrhythmias. 

The loss of sinus rhythm with subsequent junctional escape rhythm leads to AV asynchrony, which may well have greater adverse consequences for the patient with Fontan circulation, or the patient with significant systemic ventricular dysfunction, that would be the case in a patient with an otherwise normal heart. In a patient with borderline hemodynamic function, it is reasonable to consider permanent pacing to restore AV synchrony, even if a more obvious indication such as syncope or chronotropic incompetence is not present. 

Ventricular Usually 40 to 60 beats/minute In an Intra-nodal block (a junctional escape rhythm)... 

Cardiovascular Propafenone may elevate the pacing threshold of the myocardium and result in pacemaker exit blocks. In the reported case, a higher dose of propafenone (300mg twice a day) induced a loss of atrial capture with subsequent S5mcope at slow junctional escape rhythm. Both entrance and exit block was demonstrated and persisted for a longer period of time [29]. 

The safety and efficacy of mibefradil in association with beta-blockers was assessed in 205 patients with chronic stable angina, randomized to placebo or mibefradil 25 or 50 mg/day for 2 weeks (6). Besides an improvement in angina with mibefradil, it dose-dependently reduced heart rate and increased the PR interval. One patient taking mibefradil had an escape junctional rhythm 26 hours after the last dose of 50 mg. The nodal rhythm disappeared on withdrawal of mibefradil, but based on the overall results it was concluded that mibefradil was safe and effective when given for a short time with beta-blockers. 

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