The central venous blood temperature as a guide for rate control in pacemaker therapy.

True physiologic pacing is only feasible in patients with heart block and normal sinus rhythm using atrial synchronized pacing. In sick sinus syndrome (SSS) or atrial fibrillation no adequate sensing possibility is present. For these conditions something other than electrical signals must be found to guide rate control. In clinical experiments a thermistor integrated in a bipolar pacing lead was implanted in one of the authors as well as in a pacemaker patient. Treadmill tests at 3, 6, and 10 km per hour have shown no substantial increase of the central venous temperature (CVT) in the lower effort range; an increase of 0.6-0.75 degrees Celsius (degrees C) in the medium range; and an increase of 1.35 degrees C in the higher range, respectively. External pacing in the author, or rate variations by programming the VVI, M unit in the patient at rest do not influence CVT. CVT correlates well in the medium-range group, which mostly reflects the capabilities of the average pacemaker patient. In the higher effort range a delay between rate increase and increase of CVT is noticed. There is no increase in CVT beyond the physiologic variations in the lower effort range.