Reflexión arterial precoz y extrasistolia ventricular. Un mecanismo novel detectado por esfigmoquinetocardiografÝa / Early arterial reflexion and ventricular extrasystole. A novel mechanism detected with sphygmokinetocardiography

ANTECEDENT: Through sphygmokynetocardiography (SKCG) an exploratory method that records an electrocardiographic signal, a carotid pulse (CP), and two vibriograms (kinetocardiograms) of the left ventricle (LV) recorded in the left hemithorax (anterior kinetocardiogram, AKC) and the subcostal region of left abdomen (posterior kinetocardiogram of PKC, vibrations transmitted through the hemidiaphragm) we observed a systolic precocious reflection wave (Rw) in the CP and prolongation of LV ejection time (LVET) measured in AKC or in PKC of the previous sinusal pre-extrasystolic beat (PEB) vs control beats (CB) in cases with ventricular extrasystoles (VEs). OBJECTIVE: To demonstrate whether the intervals just mentioned are associated with ventricular extrasystoles. METHOD: Sixty cases: 30 with VEs, group A, and 30 without arrhythmia, group B, were studied through SKCG. The LVET and the arterial reflection index or ARI = Ta-rw/LEVT, Ta-rw = time between initial ventricular impulse to reflexive wave, were measured. RESULTS: Demography was similar in both groups. PEB had a longer LVET than the CB (291 +/- 41 vs 279 +/- 39, p < 0.01) and ARI was shorter (0.36 +/- 0.17 vs 0.58 +/- 0.21, p < 0.001). CONCLUSIONS: 1) Distention of the LV due to Rw, possibly through the well-known experimental mechanism of electromechanic feedback, is believed to underlie the arrhythmia. 2) The observation has important clinical implications.

Efecto de la contracción muscular en la frecuencia cardiaca y en el flujo sanguÝneo cutßneo / Resultados preliminares. Effect of muscle contraction on heart rate and skin blood flow. Preliminary results

Evaluation of heart rate variability is an important tool to study several diseases. The most important tests include the variability of the heart rate as a function of time and as function of frequency, variability of blood pressure and pulsatile cutaneous blood flow (PCBF). We studied the effect of a sustained contraction of the quadriceps muscle on the instantaneous heart rate and pulsatile cutaneous blood flow in 10 healthy subjects. We measured the R-R interval and the instantaneous heart rate, in the time domain, 10 beats before the contraction, the R-R interval that coincided with the onset of the contraction, and the 30 R-R intervals after the beginning of the contraction. To measure the PCBF we used a photopletismograph designed for this purpose. We recorded the surface electromyographic activity (EMG) of the quadriceps muscle to determine the onset and end of the muscle contraction, and measured respiratory movements with a belt. We found an increase of the instantaneous heart rate at the first and second beats after the onset of the contraction. There was a decrease of the pulsatile cutaneous blood flow of the finger pad immediately after the contraction, which lasted for approximately eight beats. The findings support the idea of a central command and co-activation of the motor and sympathetic nervous systems. This efferent sympathetic activity seems to act not just on the contracting muscle but also on the heart and the cutaneous blood vessels of the extremities. These findings imply that it is quite likely that the sympathetic efferent effect has a supraspinal origin. This is a test that could be used to study cardiovascular control by the sympathetic nervous system.