Mechanocardiographic effects of an elevated central venous pressure.

Since 1985 we demonstrated that the increase of left ventricular mean diastolic pressure shortens the interval existing between the onset of the electrocardiographic P-wave and the onset of the left apexcardiographic "a"-wave (Aubert et al., 1981; Mortarino et al., 1985). In particular we showed that left P-"a" time interval shortens below 100 msec when left ventricular mean diastolic pressure rises above 12 mmHg. Our results thus substantiated the previous reports related to the P-4th heart sound shortening and 4th heart sound--1st heart sound increase occurring in patients with left ventricular failure (Shapira et al., 1982). In that same period, Kesteloot and collaborators showed a direct relationship between the velocity of appearance of the right internal jugular pulse (JVP) waves and the value of central venous pressure (CVP) (Minten et al., 1985). Moreover the range of variability of the right P-"a" interval (which is the time elapsing between the onset of the electrocardiographic P-wave and the onset of the "a"-wave on the JVP tracing) is, in adult subjects, of similar magnitude of the left P-"a" interval (respectively 60-140 msec (Fishleder, 1968) and 80-160 msec (Mortarino et al., 1985) suggesting a symmetric effect of an elevation of diastolic pressure on left and right P-"a" intervals. We therefore decided to test this hypothesis in a group of patients.

Reliability of standard apexcardiography for the measurement of sudden variations in mean pulmonary capillary wedge pressure.

We simultaneously registered the left apexcardiogram together with the left intraventricular pressure curve immediately before and after ventricular angiography in order to evaluate whether the relation existing between apexcardiographic protodiastolic filling period duration (cR interval) and left ventricular mean diastolic pressure (LVMDP) was maintained even in the presence of sudden variations of LVMDP. Administration of contrast media resulted in a significant increase of LVMDP (from 11.8 to 23.9 mm Hg) and in a simultaneous decrease of the cR interval (from 108.5 to 71.0 msec) and noninvasive LVMDP calculated as 36-0.24* cR closely correlated with the invasive values both before and after angiography (overall correlation r = 0.94). Apexcardiography thus confirms to be the only highly reliable noninvasive technique which can be used by the clinical cardiologist to measure LVMDP and/or mean pulmonary capillary wedge pressure.

Mechanocardiographic effects of ACE-inhibitors.

Twenty-one subjects who suffered a recent medium sized anterior myocardial infarction conditioning a mild congestive heart failure were randomly allocated to treatment with captopril (25 mg b.i.d., 10 pts) or placebo (11 pts). After 2 months of therapy the group on the active treatment showed a significant increase of apexcardiographic protodiastolic filling period duration reflecting a clear cut decrease of mean pulmonary capillary wedge pressure (from 14 +/- 2 to 7 +/- 3 mm Hg) while patients on placebo did not show any difference in respect to baseline. Neither treatment significantly modified the PEP/LVET ratio despite a significant increase of left ventricular ejection fraction in patients receiving captopril (from 37 +/- 4% to 43 +/- 5%). Cardiac response to ACE-inhibitors can thus be noninvasively monitored by apexcardiography.

Evaluation of noninvasive alternatives to right heart catheterization.

We mechanocardiographically evaluated 50 patients with acute myocardial infarction, invasively monitored by Swan-Ganz catheters, in order to assess if mechanocardiography could provide reliable hemodynamic informations. The last 25 subjects were also studied by pulsed Doppler echocardiography. Our results confirm the high precision of apexcardiography in assessing mean pulmonary capillary wedge pressure (r = 0.91) while Doppler echocardiography proved itself better than mechanocardiography in assessing cardiac output (r = 0.82 vs r = 0.78). Moreover, Doppler echocardiography allowed a good estimation of mean pulmonary artery pressure (r = 0.81) which cannot be assessed by other noninvasive methods. However, we could not find any clinically useful relationship between Doppler mitralic flow characteristics and mean pulmonary capillary wedge pressure. Therefore noninvasive methods could represent a valid alternative to right heart catheterization provided that an integrated Doppler echocardiographic and mechanocardiographic approach is used.