Noninvasive evaluation of contractile state by left ventricular dP/dtmax divided by end-diastolic volume using continuous-wave Doppler and M-mode echocardiography

Associations of increased arterial stiffness with left ventricular ejection performance and right ventricular systolic pressure in mitral regurgitation before and after surgery: Wave intensity analysis

Background

The effect of increased arterial stiffness on mitral regurgitation (MR) is not clear. Using wave intensity (WI) analysis, which is useful for analyzing ventriculo-arterial interaction, we aimed to elucidate associations of increased arterial stiffness with left ventricular (LV) ejection performance and right ventricular systolic pressure (RVSP) in MR.

Methods and Results

We noninvasively measured carotid arterial WI and stiffness parameter (β) in 98 patients with non-ischemic chronic MR before and after surgery, and 98 age-and-gender matched healthy subjects by ultrasonography. WI is defined as WI = (dP/dt)(dU/dt) [P: blood pressure, U: velocity, t: time]. The peak value of WI (W₁) increases with LV peak dP/dt. The temporal WI index (Q-W₁)st, which is the standardized interval between the Q wave of the ECG and W₁, is a surrogate for preejection period. Ejection fraction (EF), left atrial volume index (LAVI), effective regurgitant orifice area (ERO), RVSP, and other echocardiographic data were also obtained. W₁ was enhanced in the MR group before surgery compared with the normal group (10.7 ± 5.7 vs 8.5 ± 3.6 × 10³ mmHg m/s³, p < 0.05). However, the results of two-way ANOVA showed this enhancement of W₁ was observed only in the subgroup of MR before surgery with lower arterial stiffness (β < 13, p< 0.0001). ERO, β and LAVI were predictor variables before surgery to determine RVSP. EF and (Q-W₁)st before surgery were predictor variables for EF after surgery.

Conclusions

In the MR group before surgery, increased arterial stiffness suppresses compensatory enhancement of W₁, and increases RVSP. Prolonged (Q-W₁)st has the potential for predicting low EF after surgery.

Non-invasive method for rapid bedside estimation of inotropy: theory and preliminary clinical validation

BACKGROUND

There are numerous techniques which attempt to quantify inotropy (or myocardial contractility). None has yet found general acceptance in anaesthesia and critical care as a practical method. We report a novel approach to the determination of inotropy as a bedside procedure which could identify low inotropy states in patients with clinical heart failure.

METHODS

We estimated the potential and kinetic energy delivered by the left ventricle using continuous-wave Doppler ultrasound (ultrasonic cardiac output monitor, Uscom, Sydney, Australia) and data available at the point of care. A formula to calculate effective inotropy [Smith-Madigan inotropy index (SMII)] was tested against historical haemodynamic data for 250 control subjects (ASA I patients from preoperative clinic) and 83 patients with acute left ventricular failure (LVF) of New York Heart Association Grade 4 (LVF group). The ratio of potential to kinetic energy (PKR) was investigated as a measure of arterial impedance.

RESULTS

Significant differences were found between the control and LVF groups for cardiac index, mean (range)=3.37 (2.84-5.32) vs 1.84 (1.43-2.26) litre min(-1) m(-2); stroke volume index (SVI), 49.2 (39-55) vs 34.3 (23-37) ml m(-2); systemic vascular resistance, 893 (644-1242) vs 1960 (1744-4048) dyn s cm(-5); SMII, 1.78 (1.35-2.24) vs 0.73 (0.43-0.97) W m(-2); and PKR, 29:1 (24-35:1) vs 124:1 (96-174:1), P<0.001 in each case. Normal ranges were calculated for SMII and PKR as mean (+/-1.96) standard deviations, yielding 1.6-2.2 W m(-2) for SMII, and 25-34:1 for PKR.

CONCLUSION

The method clearly identified the two clinical groups with no overlap of data points. The discriminant power of SMII and PKR may offer valuable diagnostic methods and monitoring tools in anaesthesia and critical care. This is the first report of normal ranges for SMII and PKR.

Comparison Between the Mean dP/dt During Isovolumetric Contraction and Other Echocardiographic Indexes of Ventricular Systolic Function

Echocardiographic assessments of ventricular function derived from estimates of the mean dP/dt during isovolumetric contraction (mean dP/dt(ic)) were compared with those obtained from measurements of the shortening fraction and the stress-velocity index (SVI). Mean dP/dt(ic) correlated well with the shortening fraction, r = 0.74, P < 0.0001. Furthermore, 10 out of 11 patients with mean dP/dt(ic) below 800 had a shortening fraction < 0.28, whereas all patients with a mean dP/dt(ic) > 1000 mmHg/sec had a shortening fraction > 0.28. A good correlation also existed between mean dP/dt(ic) and the SVI, r = 0.73, P < 0.0001. Nine out of 11 patients with a mean dP/dt(ic) < 800 mmHg/sec had an SVI > 2 standard deviations below normal, whereas all patients with mean dP/dt(ic) > 1000 mmHg/sec had normal or increased SVI. The correlation between mean dP/dt(ic) and the SVI was strengthened when mean dP/dt(ic) was adjusted for heart rate and preload. Hence, assessments of ventricular function derived from measurements of mean dP/dt(ic) appear to agree well with those provided by the shortening fraction and SVI. Because the determination of mean dP/dt(ic) is not hampered by unusual anatomy or wall motion (conditions which compromise the validity of the shortening fraction and SVI), mean dP/dt(ic) may be a good index of ventricular function in cases where measurements of the shortening fraction and SVI would be unreliable.