Atrial flutter in a newborn with transposition of great vessels

ECG 11A: Sinus rhythm of 156 beats/minute; probable right atrial enlargement with tall and peaked P wave in lead II; normal PR interval; right ventricular hypertrophy with systolic overload (large R waves throughout the precordium, right axis, inverse T wave in V6);

This young patient underwent arterial switch surgery after 6 days of life; in post-surgery, evidence of a supraventricular rhythm disorder;

ECG 11B: Non-sinus rhythm; tachycardia of 200 beats/minute; common flutter pattern with regular atrial activity of 400 beats/minute; characteristic sawtooth pattern in inferior leads; ventricular rhythm of 200 beats/minute with 2:1 conduction;

ECG 11C

ECG 11C: Following surgery, temporary electrodes were left in place on the atrial mass; a rapid pacing of the atrium (pacing stimuli of over 400 beats/minute) enabled a return to sinus rhythm;

Comments: In the transposition of great vessels, the aorta is in anterior position and emerges from the right ventricle, the pulmonary artery is in posterior position and emerges from the left ventricle. These anatomical and hemodynamic conditions explain the electrical characteristics visualized on the electrocardiogram at birth: 1) right ventricular pressure is high and equals systemic pressure. There is therefore a right ventricular systolic overload and a frequent overload of the right atrium; 2) left ventricular pressure can be lower than right ventricular pressure if the ventricular septum is intact and pulmonary arterial resistances are low; there is hence virtually never any left systolic overload.

In patients with transposition of large vessels and interventricular communication, certain specificities can be noted on the electrocardiogram: right ventricular hypertrophy is generally less apparent, with R or Rs complexes observed in right precordial leads and a predominant negative deflection in left-sided leads (rS complex); a suspected associated left ventricular hypertrophy can sometimes be observed given the presence of deep q waves or negative T waves in the left precordial leads;

The second tracing shows an example of a common atrial flutter in infants. It is not uncommon to observe a very rapid atrial rate (between 350 and 400 bpm) with the possibility of rapid atrioventricular conduction favoring the occurrence of cardiac decompensation. The postoperative context is conducive to the occurrence of rhythm disorders; the temporary pacing electrodes can be very useful in this setting allowing a termination by overdriving (rapid pacing) of regular and organized arrhythmias.

Take-home message: The velocity of the atrial cycle is dependent on several factors: atrial size (very fast cycles in the newborn, slower cycles in the patient with major atrial dilatation), drug therapy aimed at slowing myocardial conduction and prolonging the cycle.