Table 1. Comparison of devices used to diagnose arrhythmias, with supporting evidence of the atrial and ventricular arrhythmias found in PPCM.

	ECG		Ambulatory ECG monitoring			Cardioverter-defibrillator devices
	12-lead ECG		Continuous monitoring (e.g., Holter ECG)	Intermittent monitoring (e.g., implantable loop recorder)		Wearable cardioverter-defibrillator (WCD)	Implantable cardioverter-defibrillator (ICD)
Length of recording	10 seconds		Usually 24 or 48 hours, though newer devices can monitor up to 60 days	Up to three years (depending on the battery leave of the device)		As long as wearable cardioverter-defibrillator is worn	As long as battery life of implanted cardioverter-defibrillator lasts
Purpose of device	Diagnostic		Diagnostic	Diagnostic		Therapeutic, but also provides diagnostic information	Therapeutic, but also provides diagnostic information
Application	Non-invasive		Non-invasive	Invasive		Non-invasive	Invasive
Arrhythmias diagnosed	Whereas sinus tachycardia is common at time of diagnosis, sinus arrhythmia becomes more prevalent at follow up (19-21). While sinus tachycardia is associated with poor outcome, sinus arrhythmia predicts freedom of death and readmission to hospital (20). Prolonged QTc at time of diagnosis is associated with poor outcome (thought to be related to increased risk of ventricular arrhythmias) (20). Atrial fibrillation and LBBB, which are more prevalent in other forms of non-ischaemic dilated cardiomyopathy, seem to be uncommon in PPCM (20,22,23). AV block SVT and VT are rarely diagnosed by 12-lead ECG in PPCM (19-21)		Literature confined to a single study on 19 patients: sinus tachycardia found in 89% and non-sustained ventricular tachycardia in 21% of patients (24)	To the best of our knowledge, there is no literature available on external or implantable loop recorders in PPCM		WCD for primary prevention of SCD used in patients with LVEF <35%: though Saltzberg et al. (25) detected no arrhythmias, Duncker et al. (17,18) reported in two studies that the WCD could detect non-sustained ventricular tachycardia and ventricular fibrillation, which were successfully aborted by the WCD	ICD for primary prevention of SCD used in patients with LVEF <35%. A single study reports that 37% of patients had appropriate shocks (26)

ECG, electrocardiogram; LBBB, left bundle branch block; LVEF, left ventricular ejection fraction; PPCM, peripartum cardiomyopathy; QTc, corrected QT interval; SCD, sudden cardiac death; SVT, supraventricular tachycardia; VT, ventricular tachycardia.