Risk factors for sudden cardiac death to determine high risk patients in specific patient populations that may benefit from a wearable defibrillator

Table 5 Risk factors for sudden cardiac death in the long QT syndrome

Risk factor studied	Relative risk of SCD	P value	Absolute SCD risk in cohort	Study size	Year	Country
Female gender
Sauer et al[55]	HR 2.68 (1.10–6.50)	< 0.05	Risk between ages of 18-40: LQTS1 4.9%; LQTS2 8.0%; LQTS3 4.9%	812	2007	USA
QTc interval
Sauer et al[55]	HR 3.34 (1.49–7.49) (QTc 500–549 ms vs ≤ 499 ms)	< 0.01	Risk between ages of 18-40: LQTS1 4.9%; LQTS2 8.0%; LQTS3 4.9%	812	2007	USA
Sauer et al[55]	HR 6.35 (2.82–14.32) (QTc ≥ 550 ms vs ≤ 499 ms)	< 0.01	Risk between ages of 18-40: LQTS1 4.9%; LQTS2 8.0%; LQTS3 4.9%	812	2007	USA
Moss et al[56]	HR 1.05 (1.02-1.09) (QTc per 0.01 units)	< 0.01		1496	1991	USA
Priori et al[57]	RR 5.34 (2.82-10.13) [QTc in the third quartile (469 to 498 ms)]		Risk between ages 12-40 was 13% over 28 years	580	2003	Italy
Priori et al[57]	RR 8.36 (2.53-27.21) [QTc in the highest quartile (more than 498 ms)]		Risk between ages 12-40 was 13% over 28 years	580	2003	Italy
Goldenberg et al[58]	HR 36.53 (13.35–99.95) (LQTS with prolonged QTc interval vs unaffected family members)	< 0.001		3386	2012	USA, Europe, Japan and Israel
Goldenberg et al[58]	HR 10.25 (3.34–31.46) (LQTS with normal-range QTc interval vs unaffected family members)	< 0.001		3386	2012	USA, Europe, Japan and Israel
Previous history of cardiac events
Sauer et al[55]	HR 5.10 (2.50–10.39) (Interim time dependant syncope vs no interim syncope)	< 0.01	Risk between ages of 18-40: LQTS1 4.9%; LQTS2 8.0%; LQTS3 4.9%	812	2007	USA
Moss et al[56]	HR 3.10 (1.30-7.20) (History of cardiac event)	< 0.01		1496	1991	USA
Genotype
LQTS 3
Priori et al[57]	RR 2.76 (1.01-7.51) (Male sex)		Risk between ages 12-40 was 13% over 28 years	580	2003	Italy
Priori et al[57]	RR of 1.80 (1.07-3.04) (mutation at the LQT3 locus)		Risk between ages 12-40 was 13% over 28 years	580	2003	Italy
LQTS 2
Priori et al[57]	RR 1.61 (1.16-2.25) (LQT2 locus)		Risk between ages 12-40 was 13% over 28 years	580	2003	Italy
LQTS 1
Goldenberg et al[58]	HR 9.88 (1.26–37.63) (LQTS 1 mutation and normal QTc)	0.03		3386	2012	USA, Europe, Japan and Israel
Heart rate
Moss et al[56]	HR 1.02 (1.00-1.03) (Resting heart rate less than 60 beats/min)	0.01		1496	1991	USA
Niemeijer et al[59]	Bazett: HR 2.23 (1.17-4.24) Fridericia: HR 6.67 (2.96-15.06) (Consistent Qtc interval prolongation)			3484	2015	Netherlands

SCD: Sudden cardiac death; LQTS: Long QT syndrome; QTc: QT corrected interval; HR: Hazard ratio; OR: Odds ratio; LV: Left ventricular; EF: Ejection fraction.