Cardiac reflections and natural vibrations: force-frequency relation recording system in the stress echo lab.
BACKGROUND
The inherent ability of ventricular myocardium to increase its force of contraction in response to an increase in contraction frequency is known as the cardiac force-frequency relation (FFR). This relation can be easily obtained in the stress echo lab, where the force is computed as the systolic pressure/end-systolic volume index ratio, and measured for increasing heart rates during stress. Ideally, the noninvasive, imaging independent, objective assessment of FFR would greatly enhance its practical appeal.


OBJECTIVE
1 - To evaluate the feasibility of the cardiac force measurement by a precordial cutaneous sensor. 2 - To build the curve of force variation as a function of the heart rate. 3 - To compare the standard stress echo results vs. this sensor operator-independent built FFR.


METHODS
The transcutaneous force sensor was positioned in the precordial region in 88 consecutive patients referred for exercise, dipyridamole, or pacing stress. The force was measured as the myocardial vibrations amplitude in the isovolumic contraction period. FFR was computed as the curve of force variation as a function of heart rate. Standard echocardiographic FFR measurements were performed.


RESULTS
A consistent FFR was obtained in all patients. Both the sensor built and the echo built FFR identifiy pts with normal or abnormal contractile reserve. The best cut-off value of the sensor built FFR was 15.5 g * 10-3 (Sensitivity = 0.85, Specificity = 0.77). Sensor built FFR slope and shape mirror pressure/volume relation during stress. This approach is extendable to daily physiological exercise and could be potentially attractive in home monitoring systems.
Bombardini
Tonino
T
Department of Echocardiography (Echo Lab), IFC, CNR, Pisa, Italy. tbombardini@yahoo.it
Gemignani
Vincenzo
V
Bianchini
Elisabetta
E
Venneri
Lucia
L
Petersen
Christina
C
Pasanisi
Emilio
E
Pratali
Lorenza
L
Pianelli
Mascia
M
Faita
Francesco
F
Giannoni
Massimo
M
Picano
Eugenio
E
D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D002304:Cardiac Pacing, Artificial; D009202:Cardiomyopathies / Q000000981:diagnostic imaging / Q000503:physiopathology; D025401:Echocardiography, Stress; D005080:Exercise Test / Q000379:methods; D005240:Feasibility Studies; D005260:Female; D006331:Heart Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology*; D013318:Stroke Volume; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*