Reduced cardiac function (EF <40%) was associated with a significantly greater variation in evoked QT interval across different AV delays compared to normal cardiac function (7.6 vs 2.7 ms, p<0.05).
Observational (n=13)
Single-blind
No
Does variation in atrioventricular delay affect evoked QT intervals differently in patients with reduced versus normal cardiac function?
Changes in evoked QT intervals according to AV delay variation are greater in patients with reduced cardiac function, allowing easier determination of optimal AV delay.
Absolute Event Rate: 7.6% vs 2.7%
p-value: p=<0.05
In patients with implanted DDD pacemaker, cardiac output is maximal when atrioventricular (AV) delay is set to give the maximum QT interval (QTI). QTI is used as a sensor of a rate-responsive pacemaker and the evoked QTI (eQTI) is measured as the time duration from the ventricular pace-pulse and the T sense point, which is the steepest point of the intracardiac T wave. The relationship between the changes in eQTI according to AV delay variations and cardiac function was studied in 13 patients (74.2+/-9.3 SD years old) with an implanted QT-driven DDDR-pacemaker. A special software module was downloaded into the pacemaker memory and a personal computer equipped with the special software was connected to the programmer for eQTI date-logging. AV delay was set at 100, 120, 150, 180 and 210 ms. Delta eQTI was defined as maximal eQTI - minimal eQTI. The ejection fraction (EF) was measured by echocardiography. When the AV delay was prolonged, eQTI gradually increased and reached a peak, and then decreased. Delta eQTI in patients with reduced cardiac function (EF 55%, 7.6+/-4.9 vs 2.7+/-9.8 ms, p<0.05). There was significant negative correlation between EF and delta eQTI (r=-0.63, p<0.05). The peak of changes in eQTI according to AV delay variations was steeper in patients with reduced cardiac function than in those with normal cardiac function. In conclusion, changes in eQTI according to AV delay variation are greater in patients with reduced cardiac function than in those with normal cardiac function, and the AV delay that gives the maximal eQTI can be easily determined in patients with reduced cardiac function.
Ishikawa et al. (Wed,) conducted a observational in Complete AV block (n=13). Reduced cardiac function (EF <40%) vs. Normal cardiac function (EF >55%) was evaluated on Delta evoked QT interval (maximal eQTI - minimal eQTI) (p=<0.05). Reduced cardiac function (EF <40%) was associated with a significantly greater variation in evoked QT interval across different AV delays compared to normal cardiac function (7.6 vs 2.7 ms, p<0.05).