The timing of onset of mechanical systole and diastole in reference to the QRS-T complex: a study to determine performance criteria for a non-invasive diastolic timed vibration massage system in treatment of potentially unstable cardiac disorders.

Our institution is in development of a low frequency, non-invasive Diastolic Timed Vibrator (DTV) for use in emergency treatment of ST Elevation Myocardial Infarction (STEMI). It is preferable to avoid vibration emissions during the IsoVolumetric Contraction Period (IVCP) and at least the majority of mechanical systole thereafter, as systolic vibration may cause a negative inotropic effect in the ischemic heart. Furthermore diastolic vibration should preferably include the IsoVolumetric Relaxation Period (IVRP) which has been shown in clinical studies to improve cardiac performance and enhance coronary flow. Electrocardiographic (ECG) monitoring can be used to enable diastolic tracking, however, the timing of the phases of the cardiac cycle in relation to the ECG waveform must first be verified. The objective of this study was therefore to determine timing of onset of mechanical systole and diastole in reference to the QRS-T Complex. One hundred and twenty-three adult echocardiographic studies were assessed for the point of mitral and aortic valve closure in relation to the QRS complex and T wave in a representative population. We found that onset of mechanical systole occurred on and usually shortly after the peak of a first dominant QRS complex deflection, and onset of diastole occurred at the earliest on and most commonly beyond the peak or midpoint of the T wave. A DTV should ideally be able to stop vibrating on or before the peak of the first dominant deflection of a QRS complex, and begin vibrating near the peak of the T wave. Given early detection of ventricular depolarization can occur 10-20 ms prior to R wave peak, it is proposed that a DTV should preferably be able to stop vibrating within 10 ms of a triggered stop command. Onset of vibration during peak of T wave could be approximated by a rate adapted Q-T interval regression equation, and then fine tuned by manual adjustment during therapy.