Table 1.

The clinical characteristics and summary of included studies

Study	Debonnaire et al. (2015)	Femenia et al. (2013)	Kang et al. (2014)	Nomura et al. (2015)	Ozyilmaz et al. (2017)
Country	The Netherlands	Argentina, Spain, Belgium, Turkey, Venezuela, and Canada	South Korea	Japan	Turkey
Study design	Prospective cohort	Retrospective cohort	Retrospective cohort	Retrospective cohort	Prospective cohort
Year of publication	2015	2013	2014	2014	2017
Study subjects	HCM patient at Leiden University Medical Centre, The Netherlands	HCM patient with ICD implanted for primary or secondary prevention	HCM patient diagnosed from echocardiography between Feb 2001 and Apr 2007	HCM patient followed at the Kanazawa University Hospital and its affiliated hospitals from Sep 2008 to Mar 2010	HCM patients aged more than 17 who presented to the Mehmet Akif Ersoy Thoracic and Cardiovascular surgery Center, Training and Research Hospital and Bezmialem Vakif University School of Medicine between Dec 2012 and Mar 2016
Exclusion criteria	HCM patients with ventricular pacing or bundle branch block at baseline ECG	N/A	Reduced LV function (LVEF <50%), QRS ≤120 ms, left or right bundle branch block, previous ICD placement (n and age <18 years	Unable to obtain appropriate ECG data at registration, clinical data missing, diagnosed with cardiac sarcoidosis after registration	Patients with previous history of aborted SCD or those who had previously undergone ICD implantation
					Patients with history of septal ablation or myomectomy
					Patients with hypertension, renal failure, history of MI or aoritic valve stenosis
Number of subjects (% male, mean age)	195 patients (61% male, mean age 52 ± 13 years)	102 patients (52% male, mean age 41.16 ± 18.25 years)	273 patients (57% male, mean age 55 years)	94 patients (60% male, mean age 58 ± 17 years)	115 patients (58% male, mean age 46.5 ± 15.3 years)
Number of fQRS subjects	145	54	67	31	65
Number of non‐fQRS subjects	50	48	100	63	50
Median LV wall thickness (mm)	21	24.79 ± 7.65	21 ± 4	17 ± 5	N/A
Mean QTc duration (msec)	427 ± 28	430.38 ± 22.98	438 ± 29	436 ± 36	N/A
LA size (mm)	N/A	42.72 ± 9.66	N/A	N/A	41.9 ± 4.3
Hx of Non‐sustained VT	52	39	N/A	N/A	N/A
Unexplained syncope	17	60	15	N/A	13
Family Hx SCD	91	33	33	11	48
Prior personal history of SVT/VF/SCD	13	43	N/A	7	N/A
Abnormal BP during exercise	N/A	13	N/A	N/A	N/A
ICD implantation at baseline	58	102	N/A	7	11
fQRS definition criteria	Presence of various RSR′ patterns, notching in the R or S wave or presence of >1 additional R in ≥2 beats of a non‐aVR lead.	Presence of various RSR′ patterns, which included an additional R′ or notching of the R‐wave, notching of the down‐ or upstroke of the S‐wave, or the presence of >1R′ in two contiguous leads.	Presence of an additional R′, notching in the nadir of the R or S wave, or the presence of >1 R′ in 2 contiguous leads that corresponded to a single myocardial territory.	QRS duration <120 ms	Presence of R′ with or without a Q wave on 12‐lead ECG, the presence of notching on an R wave, the presence of notching on an S wave, or the presence of more than one R′ wave in two adjacent derivations corresponding to the feeding area of one of the major coronary arteries
				R′, notching in nadir of the S wave, notching of R wave, or >1 R′ in 2 contiguous leads
				In patients with right or left bundle branch block (QRS duration ≥120 ms)
				RsR′ pattern with or without a Q wave, >2 notches in the R wave, >2 notches in the downstroke or upstroke of the S wave, in two contiguous leads
				Patients with mechanical pacing (QRS duration ≥120 ms)
				>2 R′ or >2 notches in the S waves in two contiguous leads
Endpoints	Occurrence of malignant sustained VT, VF, or SCD	Appropriate ICD therapies (sustained VT or VF)	Major arrhythmic events (sustained VT and SCD)	Major arrhythmic event (sudden cardiac death, sustained VT and VF)	Sudden cardiac death
Mean follow‐up	Median 5.7 years (IQR 2.7–9.1)	47.9 ± 39.3 months	6.3 years	4 years	5 years
Conclusion	Extensive fQRS is associated with sustained VT/VF and or SCD in HCM patients.	fQRS is associated with a significant increase in arrhythmic events in HCM patients with ICD implant.	The presence of an fQRS, in particular in the inferior leads, wassignificantly associated with a higher risk of fetal ventricular arrhythmia events in HCM patients	fQRS is significantly associated with heart failure with hospitalization and lower heart failure‐free survival in HCM patient	fQRS significantly increase risk of ventricular arrhythmias and SCD in HCM patients. fQRS is an independent high‐risk indicator of SCD in HCM

Bold terms indicate subgroup definition. ECG, electrocardiogram; fQRS, fragmented QRS; HCM, hypertrophic cardiomyopathy; ICD, implantable cardioverter defibrillator; IQR, Interquartile range; N/A, not applicable; SCD, sudden cardiac death; VF, ventricular fibrillation; VT, ventricular tachycardia.