MICROANATOMY

Detailed explanation-1: -Spontaneous diastolic depolarization is a normal property of SA nodal, AV nodal, and Purkinje cells, but not atrial or ventricular myocytes except under pathophysiological conditions.

Detailed explanation-2: -Diastolic depolarization is defined as activity on the isopotential map that can be continuously tracked back in time from VT exit sites, defined on the map as synchronous with the QRS onset.

Detailed explanation-3: -Phase zero is the phase of depolarization. This phase starts when the membrane potential reaches-40 mV, the threshold potential for pacemaker cells. There is the opening of voltage-gated Ca2+ channels on reaching the threshold, causing the influx of Ca2+ ions.