Sotalol Overdose

Report:

Sinus rhythm 62/min

2:1 AV block

Ventriculophasic sinus arrhythmia

Prolonged QT interval 0.58”

QTc 0.58”

Comment:

The blocked alternate P waves are not very obvious, superimposed on prolonged, themselves rather wavy, T waves. Also, alternate atrial cycles, those containing a QRS complex, are shorter, due to the ventriculophasic effect. Lead V1-2 are best, with small T waves and fairly sharply notched P waves – Marriott’s haystack principle61. Once identified, blocked P waves become obvious in lead 2 rhythm strip where, initially, they seem to be part of the bizarre TU wave.

Interestingly, the AV block lifted but sinus bigeminy persisted (Fig 86a). The ventriculophasic sinus arrhythmia may not have caused, therefore, to original cycle length alternation. A 3:2 SA block or some other, unknown mechanism, may be responsible. The shortest cycle in the middle of the tracing (also with longer PR interval) may be a SVEB, perhaps even a sinus extrasystole.

Sotalol, unlike other ß-blockers, behaves like a Class III antiarrhythmic and prolongs the QT interval, with propensity to torsades and sudden death.

86a. The shortest cycle is due to a SVEB – even though its P’R interval is longer than sinus PR intervals. 87. 25 year old lady with manic-depressive psychosis, unconscious