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Rhythm abnormality seen in this ECG:
a) First degree AV block
b) Second degree AV block
c) Complete AV block
d) None of the above
Answer: c) Complete AV block
Complete heart block with narrow QRS subsidiary rhythm. Narrow QRS subsidiary rhythm occurs when the block is above the His bundle. In addition there are deep S waves in V3 and tall R waves in V5, with ST segment depression and T wave inversion in inferior and lateral leads, probably indicating left ventricular hypertrophy.
Four criteria for diagnosis of complete heart block: (1) Regular PP interval (2) Regular RR interval (3) PP interval shorter than RR interval (4) Totally varying PR interval
Leads I, II and III gives a superficial impression of 2:1 AV block, which is proved wrong by the subsequent leads. Such simulation of 2:1 AV block in short strips of a complete heart block is called “Accrochage”.