Prognosis

The risk of dying is increased with arrhythmias 

• 10 or more premature ventricular contractions per hour  ^{a b}
• ventricular fibrillation (particularly after 48 hours) ^{a   b}
• 2nd ^b or 3rd degree heart block ^{a b} after 24 hours
• cardiac arrest ^{a b}

Why?

Ventricular arrhythmias and heart block increase the risk of dying

Patient	Prognostic Factor	Outcome	CER	OR (95% CI)	NNF+ (95% CI)
myocardial infarction a	10 or more premature ventricular contractions per hour independent	death at 18 months	5.8%	6.06 (1.90 to 19.4)	5 (2 to 21)
myocardial infarction b	complex ventricular arrhythmias independent	death at 6 months	3.0%	2.55 (1.96 to 3.32)	23 (16 to 37)
first myocardial infarction b	VF within 4 hours of infarction independent	death at uncertain duration	4.0%	2.47 (1.48 to 4.13)	19 (9 to 55)
first myocardial infarction	VF >4hrs but <48hrs after infarction independent	death at uncertain duration	4.0%	3.97 (1.51 to 10.5)	10 (4 to 52)
first myocardial infarction	VF >48hrs after infarction independent	death at uncertain duration	4.0%	20.2 (11.5 to 35.5)	2 (2 to 4)
myocardial infarction b	2nd or 3rd degree heart block independent	death at uncertain duration	4.0%	2.89 (2.03 to 4.09)	15 (9 to 26)
inferior MI a	complete heart block independent	death at 12 months	16%	2.7 (1.3 to 5.5)	5 (3 to 25)