Risk of Mortality Associated With QT and JT Intervals at Different Levels of QRS Duration (from the Third National Health and Nutrition Examination Survey)

Abstract

QT prolongation in the setting of QRS>120 ms is believed to be triggered by prolonged depolarization rather than repolarization. Hence, JT interval is suggested as an alternative to QT interval when QRS duration is prolonged. It is unclear, however, if JT and QT intervals portend similar risk of mortality for different durations of QRS. We examined the association between QT and JT, separately, with all-cause mortality across different levels of QRS duration in 8,025 participants (60±13 years, 41% white, and 54% women) from the Third National Health and Nutrition Examination Survey. At baseline (1986–1994), 486 (6%) participants had QRS duration≥120 ms. During a follow-up of up to 18 years, 3,045 (38%) deaths occurred. There were significant non-linear relationships of QT and JT intervals with mortality (p <0.001). Hence, QT and JT were categorized as prolonged (>95th percentile), shortened (<5th percentile) and normal (reference group). In multivariate adjusted Cox regression models, prolonged JT [HR (95% CI): 4.75, (1.86, 12.11)] was associated with increased risk of mortality more than prolonged QT [HR (95%CI):1.50 (1.03, 2.17)] in participants with QRS ≥120 ms (Interaction p=0.02). In participants with QRS duration <120ms, prolonged QT and JT were equally predictive of all-cause mortality [HR (95%CI): 1.27(1.06, 1.54)] and [1.31 (1.10, 1.55)], respectively. Similar patterns were observed with shortened QT and JT intervals. In conclusion, although both QT and JT intervals are predictive of mortality, JT is more predictive in the setting of QRS duration>120 ms supporting the use of JT interval in individuals with prolonged QRS.

Arrhythmogenic drugs can amplify spatial heterogeneities in the electrical restitution in perfused guinea-pig heart: An evidence from assessments of monophasic action potential durations and JT intervals

“…The assessments were based on measuring the JT rather than the QT intervals, because in the setting of delayed ventricular conduction attributable both to the epicardial pacing and Na + channel blockers effects, a wide QRS complex can significantly contribute to the overall QT duration, thus reducing its specificity in detecting repolarization derangements. Clinically, the risk of incident cardiovascular events is better predicted with measurements of the JT rather than the QT interval [ 57 – 59 ]. It is also noteworthy that in isolated, perfused hearts, the QT interval typically grossly exceeds ventricular action potential duration, and the QT is less sensitive to changes in pacing rate and drug effects, when compared to the corresponding variations in APD 90 [ 60 – 61 ].…”

Blunted Nighttime Sympathetic Nervous System Response to Stress Among Thai Men with Positive Family History of Sudden Unexplained Nocturnal Death Syndrome

“…This study did not include a direct index of malnutrition, which has been suggested as a risk factor for SUNDS. 52,53) However, the data on body mass index and the physician's examinations of the participants suggest that they were all in the normal body mass index range for their age (18.5-25 kg/m 2 ), and none of them displayed any overt signs of malnutrition in their history and physical examinations. Future studies should also monitor serum magnesium (an important contributor to cardiac function), genetic profile, electrocardiography, and direct or indirect measure of autonomic nerve activity.…”

QTc interval evaluation in patients with right bundle branch block or bifascicular blocks

“…1 The presence of a bundle branch block (BBB) represents a particular challenge in properly measuring the QTc interval. 2 Following international recommendations, QT interval should be measured in leads showing the longest QT interval, which is usually in right precordial leads. 3 In presence of a right bundle branch block (RBBB) or a bifascicular block, these leads are strongest affected by conduction delay and therefore hamper adequate measurement.…”