Experimental study of the so called left ventricular isovolumic relaxation phase.
OBJECTIVE
Left ventricular filling begins in the ventricular isovolumic relaxation phase. According to the Torrent-Guasp myocardial band theory, this phase results from the contraction of the final portion of the myocardial band: the ascending segment of the apical loop. The objectives were to study the myocardial mechanisms influencing transmitral flow during early diastole and to determine whether the rapid ventricular filling phase involves contraction or relaxation.


METHODS
An experimental in vivo pig model was used. Regional contractility in three segments of the myocardial band was assessed using piezoelectric crystals and mitral flow was measured by echo-Doppler ultrasonography at baseline and after akinesia had been induced in the ascending segment by 2.5% formaldehyde infusion. Changes in intracavitary pressure in the left ventricle and left atrium and flow alterations in the aortic root were recorded. The start of the isovolumic relaxation phase was identified using the time at which the ejection of blood ceases, as indicated by aortic flow measurements.


RESULTS
During the left ventricular isovolumetric relaxation phase, the ascending segment of the apical loop was undergoing contraction. The infusion of formaldehyde into this segment affected the extent to which the intraventricular pressure could decrease, prolonged the isovolumic relaxation phase and resulted in a lower minimum pressure. It also produced a significant decrease in transmitral flow velocity in early diastole and an increase at end-diastole.


CONCLUSIONS
The rapid ventricular filling phase is characterized by contraction.
Cosín Aguilar
Juan A
JA
Unidad de Cardiología Experimental, Centro de Investigación, Hospital Universitario La Fe, Avda. Campanar 21, Valencia 46009, Spain. hernandiz_amp@gva.es
Hernándiz Martínez
Amparo
A
Tuzón Segarra
M Teresa
MT
Agüero Ramón-Llin
Jaime
J
Torrent-Guasp
Francisco
F
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D003326:Coronary Circulation / Q000502:physiology; D018618:Echocardiography, Doppler, Color; D005260:Female; D005557:Formaldehyde / Q000633:toxicity; D008297:Male; D008943:Mitral Valve / Q000502:physiology; D009200:Myocardial Contraction / Q000502:physiology*; D013552:Swine; D016277:Ventricular Function, Left / Q000502:physiology*
D005557:Formaldehyde