Six years follow-up of an implanted SvO(2) sensor in the right ventricle.
BACKGROUND
Mixed venous oxygen saturation (SvO(2)) is a standard invasive measure used in the management of congestive heart failure patients. The reliability of a long-term SvO(2) sensor remains unproven.


METHODS
Nine patients (NYHA Class I/II, n=2/7) were implanted with a dual chamber pacemaker modified to utilize a right ventricular SvO(2) lead (Medtronic Inc., Models 8007/4327A IPG/Lead). Invasive studies compared sensor SvO(2) to reference (Optical Swan-Ganz catheter) at 0, 3 and 9 months. Symptom limited tests (Bike(max)) with metabolic assessment and arterial oxygen saturation measurements performed 1-7 days, 3.5 and 9.5 months post-implant allowed for cardiac output calculations. Long-term sensor performance was confirmed by submaximal tests, Bike(subm) in years 1-3, and Walk(in-place) every 6 months for the duration of follow-up.


RESULTS
Sensor SvO(2) readings were stable over time when compared to the Swan-Ganz Catheter. Non-invasive CO measured during Bike(max) was in normal ranges for this patient population, 3.7+/-0.9 l/min at rest and 8.4+/-2.2 l/min at peak-exercise. Resting SvO(2) values from Bike(subm) and Walk(in-place) did not change significantly over time (P>0.1 vs. 1 year) and neither did the change from rest to peak exercise during Bike(subm) (P>0.05 vs. 1 year) or Walk(in-place) (P>0.05 vs. 4 year).


CONCLUSIONS
While limited in size, this small pilot study suggests that long-term monitoring of SvO(2) by implanted devices may be feasible. The clinical value remains to be proven in future studies.
Heart Failure Management, Medtronic Inc., MS CW210, Minneapolis, MN 55432, USA. barbro.kjellstrom@medtronic.com
Barbro
B
Kjellström
Cecilia
C
Linde
Tom
T
Bennett
Ake
A
Ohlsson
Lars
L
Ryden
D000368:Aged; D015374:Biosensing Techniques; D004567:Electrodes, Implanted; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D019736:Prostheses and Implants
D010100:Oxygen