Wenckebach Cycle Length (wenckebach + cycle_length)

Distribution by Scientific Domains


Selected Abstracts


Autonomic Blockade Unmasks Maturational Differences in Rate-Dependent Atrioventricular Nodal Conduction and Facilitation in the Mouse

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2003
SAMIR SABA M.D.
Maturational Differences in Murine AVN Conduction. Introduction: In large animals, rate-dependent AV nodal (AVN) properties of conduction are modulated by autonomic inputs. In this study, we investigated whether the properties of AVN conduction and facilitation are altered by autonomic blockade in the mouse and whether this effect is age dependent. Methods and Results: Young (age 4,6 weeks; n = 11) and adult (age 8,9 months; n = 11) female mice underwent in vivo electrophysiologic testing, before and after autonomic blockade. After autonomic blockade, the adult mice had significantly longer AVN effective refractory period (AVNERP; 67 ± 14 msec vs 56 ± 4 msec, P = 0.05) and functional refractory period (AVNFRP; 81 ± 10 msec vs 72 ± 4 msec, P = 0.05). With autonomic blockade, the increase from baseline of AVN Wenckebach cycle length (,AVW; 1.8 ± 8.1 msec vs 8.8 ± 3.3 msec, P = 0.04), as well as of AVNERP (,AVNERP; 3.5 ± 3.5 msec vs 21.4 ± 12.6 msec, P = 0.002) and AVNFRP (,AVNFRP; 2.3 ± 3.2 msec vs 12.8 ± 9.0 msec, P = 0.008), was significantly larger in adult than in young mice. Compared with young mice, adult mice were less likely to exhibit AVN facilitation (44% vs 90%, P = 0.03) and had smaller maximal shortening of AVN conduction times after the "test beat" for any coupling of the "facilitating beat" (4 ± 4 msec vs 7 ± 3 msec, P = 0.05). Conclusion: Complete autonomic blockade significantly increases AVN conduction times and refractory periods in adult but not in young mice. Adult mice also exhibit less AVN facilitation. Our results confirm that, like in larger animals, rate-dependent murine AVN properties of conduction are under autonomic regulation. Adult mice have higher sympathetic AVN inputs at baseline, leading to slower conduction after autonomic blockade. (J Cardiovasc Electrophysiol, Vol. 14, pp. 191-195, February 2003) [source]


Abnormal Atrioventricular Node Conduction and Atrioventricular Nodal Reentrant Tachycardia in Patients Older Versus Younger Than 65 Years of Age

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2009
MIHAELA GRECU M.D.
Study Objective: We examined the possible role of atrioventricular node (AVN) conduction abnormalities as a cause of AVN reentrant tachycardia (RT) in patients >65 years of age. Study Population: Slow pathway radiofrequency catheter ablation (RFCA) was performed in 104 patients. Patients in group 1 (n = 14) were >65 years of age and had AV conduction abnormalities associated with structural heart disease. Patients in group 2 (n = 90) were <65 years of age and had lone AVNRT. Results: Patients in group 1 versus group 2 (66% vs. 46% men) had a first episode of tachycardia at an older age than in group 2 (68 ± 16.8 vs 32.5 ± 18.8 years, P = 0.007). The history of arrhythmia was shorter in group 1 (5.4 ± 3.8 vs 17.5 ± 14, P = 0.05) and was associated with a higher proportion of patients with underlying heart disease than in group 2 (79% vs 3%, P < 0.001). The electrophysiological measurements were significantly shorter in group 2: atrial-His interval (74 ± 17 vs 144 ± 44 ms, P = 0.005), His-ventricular (HV) interval (41 ± 5 vs 57 ± 7 ms, P = 0.001), Wenckebach cycle length (329 ± 38 vs 436 ± 90 ms, P = 0.001), slow pathway effective refractory period (268 ± 7 vs 344 ± 94 ms, P = 0.005), and tachycardia cycle length (332 ± 53 vs 426 ± 56 ms, P = 0.001). The ventriculoatrial block cycle length was similar in both groups. The immediate procedural success rate was 100% in both groups, and no complication was observed in either group. One patient in group 2 had recurrence of AVNRT. One patient with a 98-ms HV interval underwent permanent VVI pacemaker implantation before RFCA procedure. Conclusion: In patients undergoing RFCA for AVNRT at >65 years of age had a shorter history of tachycardia-related symptoms than patients with lone AVNRT. The longer AVN conduction intervals and refractory period might explain the late development of AVNRT in group 1. [source]


Effects of Sex and Age on Electrocardiographic and Cardiac Electrophysiological Properties in Adults

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2001
TARESH TANEJA
TANEJA, T., et al.: Effects of Sex, and Age on Electrocardiographic and Cardiac Electrophysiological Properties in Adults. Although differences in patient sex in heart rate and QT interval have been well characterized, sexual differences in other cardiac electrophysiological properties have not been well defined. The study population consisted of 354 consecutive patients without structural heart disease or preexcitation who underwent clinically indicated electrophysiological testing in the drug-free state. Atrial, AV nodal, and ventricular effective refractory periods (AERP, AVNERP, VERP) were determined at a pacing cycle length of 500 ms using an 8-beat drive train and 3-second intertrain pause. There were 124 men and 230 women with a mean age of 45 ± 19 and 47 ± 18 years, respectively The sinus cycle length (SCL) was longer in men than in women (864 ± 186 and 824 ± 172 ms, respectively, P < 0.05). The QRS duration was significantly longer in men (90 ± 12 ms) than women (86 ± 13 ms) (P < 0.005). The HV interval was 48 ± 9 ms in men and 45 ± 8 ms in women (P < 0.05). The sinus node recovery time (SNRT) was significantly longer in men than in women (1215 ± 297 ms and 1135 ± 214 ms, respectively, P < 0.05). AERP and VERP were similar in both sexes. Aging did not influence sexual differences in cardiac electrophysiological properties, although, it independently prolonged the SCL, PR, and QT intervals, AH and HV intervals, SNRT, AVNERP, and the AV Wenckebach cycle length. The SCL, QRS duration, HV interval, and SNRT were significantly longer in men than in women. Aging prolonged cardiac conduction and increased the SCL but the effects were similar in both sexes. AERP and VERP were unaffected by aging or sex. [source]


Connexin40-Deficient Mice Exhibit Atrioventricular Nodal and Infra-Hisian Conduction Abnormalities

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2000
BRIAN A. VANDERBRINK B.S.
AV Nodal and Infra-Hisian Conduction in Cx40 Mice. Introduction: Previous electrophysiologic investigations have described AV conduction disturbances in connexin4(Cx40)-deficient mice. Because expression or(Cx40 occurs predominantly in the atria and His-Purkinje system of the mouse heart, the AV conduction disturbances were thought to be secondary to disruption in His-Pnrkinje function. However, the lack of a His-bundle electrogram recording in the mouse has limited further investigation of the importance of Cx40. Using a novel technique to record His-bundle recordings in Cx40-deficient mice, we define the physiologic importance of defciencies in Cx40. Methods and Results: Ten Cx40 -/- mice and 11 Cx40+/+ controls underwent a blinded, in vivo, closed chest electrophysiology study at 9 to 12 weeks of age. In the Cx40+/+ mice, the PR interval was significantly longer compared with Cx40+/+ mice (44.6 ± 6.4 msec vs 36.0 ± 4.1 msec, P = 0.002). Not only the HV interval (14.0 ± 3.0 msec vs 10.4 ± 1.2 msec, P = 0.003) but also the AH interval (33.2 ± 4.8 msec vs 27.1 ± 3.7 msec, P = 0.006), AV Wenckebach cycle lengths, and AV nodal effective and functional refractory periods were prolonged in Cx40 -/- compared with Cx40+/+ mice. Conclusion: Cx40-deficient mice exhibit significant delay not only in infra-Hisian conduction, as would be expected from the expression of Cx40 in the His-Purkinje system but also in the electrophysiologic parameters that reflect AV nodal conduction. Our data suggest a significant role of Cx40 in atrionodal conduction and/or in proximal His-bundle conduction, [source]