Peripartum cardiomyopathy (PPCM) is a rare life-threatening heart disease of still unknown cause manifested in the late pregnancy or within 5 months after delivery in women without prior known cardiac pathology. Outcome of PPCM is highly variable, comprising clinical recovery, rapid deterioration unresponsive to medical treatment requiring mechanical circulatory support and even death. Early diagnosis allows for standard heart failure treatment respecting contraindications for some drugs in pregnancy. Confirmation needs the echocardiography to reveals left ventricular dysfunction. However, the variables from the electrocardiography (ECG) like QRS duration are also important in initial assessment. This paper presents the current state of knowledge of diagnostic and prognostic role of the occurrence of left bundle branch block (LBBB) in PPCM.