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Temperature May Be an Appropriate Sensor for Chronotropically Incompetent Patients with Postural Syncope
Author(s) -
SINGER IGOR,
RIPLEY KEN,
JOHNSON BEN,
STODDARD MARGUS
Publication year - 1994
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.1994.tb02360.x
Subject(s) - medicine , chronotropic , cardiology , heart rate , stroke volume , cardiac output , cardiac function curve , heart failure , anesthesia , blood pressure , hemodynamics
Chronotropically incompetent patients benefit most from sensor driven rate response during exercise. Postural syncope may occur despite the chronotropic response because of the failure of currently available sensors to respond physiologically to postural changes. Seven chronotropically incompetent patients with postural syncope who had a dual chamber rate adaptive pacemaker (Circadia R ) that modulates heart rate in response to temperature change were studied with respect to: (1) response to exercise: and (2) head‐up tilt (HUT). During exercise, continuous‐wave Doppler of aortic velocities and two‐dimensional echocardiographic derived measurements of left ventricular systolic function were used to assess cardiac function. Patients exercised longer (by an average of 168 sec) in the DDDF/compared to the DDl mode (P = 0.013). Increase in exercise duration was due mostly to the sensor driven increase during DDDH pacing. During DDDR pacing, heart rate increased from 71 ± 6 to 121 ± 17 ppm compared to 70 ± 1 to 103 ± 21 ppm for the DDl pacing (P = 0.038). Stroke volume as assessed by Doppler derived stroke distance (SD) contributed more significantly to the cardiac output increase during exercise in the DDl mode (SD increased from 13.4 ± 4 to 18 ± 7 cm in DDl compared to 13 ± 4 to 14 ± 2 cm in DDDR mode), although these mechanisms were insufficient to fully compensate for failure of appropriate chronotropic response. In response to the HUT, right ventricular temperature increased from 36.78°C ± 0.29°C to 36.89±± 0.28°C (P = 0.0002), and heart rate increased from 54 ± 3 to 71 ± 8 ppm (P = 0.0003) in the DDDR mode. No significant change in heart rate occurred in the DDl mode in response to the HUT. Strong positive correlation of temperature and heart rate was noted in all patients in response to HUT (P = 0.001, R 2 = 0.755–0.976). We conclude that temperature sensor responds physiologically to exercise and HUT. Therefore, temperature sensing rate adaptive dual chamber pacing may be appropriate for chronotropically incompetent patients with posture related syncope.