2.2 Clinical Data and Measurements
Data collection was done by reviewing the electronic medical records.
Patient characteristics, indications, pre-implantation medical details,
electrocardiographic (ECG), echocardiographic (ECHO) findings, and
procedural details were reviewed. Intrinsic QRS duration was defined as
the duration of conducted QRS (or escape QRS in case of no conducted
beats) in the pre-implantation ECG. QRS complexes were classified
according to duration and morphology using the standard criteria
established by American Heart Association and Heart Rhythm Society
expert consensus document (11). Ejection fraction(EF) was calculated
using Simpson’s method and other echocardiographic parameters were
acquired according to American Society of Echocardiography and European
Society of Echocardiography expert consensus document (12). The site of
ventricular lead placement was ascertained from the procedural notes
which was further confirmed from chest radiograph and classified as
apical or non-apical based on the location. PM parameters were noted at
discharge and at end of follow up period. RV pacing % burden was
recorded at end of follow up period or earlier if the primary outcome of
PICM was reached. Paced QRS duration was measured from the immediate
post pacemaker insertion electrocardiogram. PICM was defined as a fall
in post implant LVEF by 10 percentage points to a LVEF of less than 50.0
% from baseline due to RV pacing in the absence of other known causes
of cardiomyopathy.