Effect of dobutamine on regional diastolic left ventricular asynchrony in patients with left ventricular hypertrophy

Diastolic dyssynchrony and its exercise-induced changes affect exercise capacity in patients with heart failure with reduced ejection fraction

BACKGROUND

Left ventricular diastolic dyssynchrony is common in patients with heart failure with reduced ejection fraction (HFREF). Little is known however, about its pathophysiology and clinical effects. Herein is hypothesized that presence of diastolic dyssynchrony at rest or at exercise may importantly contribute to HF symptoms. The aim was to investigate the influence of diastolic dyssynchrony and its exercise-induced changes on exercise capacity in HFREF patients.

METHODS

Patients with stable, chronic HF, left ventricular ejection fraction < 35%, sinus rhythm and QRS ≥ 120 ms were eligible for the study. Rest and cyclo-ergometer exercise echocardiography were performed. Diastolic dyssynchrony was defined as opposing-wall-diastolic-delay ≥ 55 ms measured in tissue-Doppler imaging. Exercise capacity was assessed by peak oxygen consumption (VO2peak). Association between diastolic dyssynchrony and VO2peak was assessed in univariate regression analysis and further adjusted for possible confounders.

RESULTS

Fourty eight patients were included (aged 63.7 ± 12.2). Twenty-seven (56.25%) had diastolic dyssynchrony at rest and 13 (27%) at exercise. Twenty-two (46%) experienced a change in diastolic dyssynchrony status during exercise. In univariate models diastolic dyssynchrony at rest or at exercise were associated with lower VO2peak (beta coefficient = -3.8, p = 0.004; beta coefficient = -3.6, p = 0.02, respectively). However, the ability to restore diastolic synchronicity during exercise was associated with higher VO2peak (beta coefficient = 3.4, p = 0.04) and remained an important predictor of exercise capacity after adjustment for age and HF etiology.

CONCLUSIONS

The ability to restore diastolic synchronicity at exercise predicts exercise capacity in patients with HFREF.

Improvement of left ventricular filling by ivabradine during chronic hypertension: involvement of contraction-relaxation coupling

Chronic hypertension is associated with left ventricular (LV) hypertrophy and LV diastolic dysfunction with impaired isovolumic relaxation and abnormal LV filling. Increased heart rate (HR) worsens these alterations. We investigated whether the I f channel blocker ivabradine exerts beneficial effects on LV filling dynamic. In this setting, we also evaluated the relationship between LV filling and isovolumic contraction as a consequence of contraction-relaxation coupling. Therefore, hypertension was induced by a continuous infusion of angiotensin II during 28 days in 10 chronically instrumented pigs. LV function was investigated after stopping angiotensin II infusion to offset the changes in loading conditions. In the normal heart, LV relaxation filling, LV early filling, LV peak early filling rate were positively correlated to HR. In contrast, these parameters were significantly reduced at day 28 vs. day 0 (18, 42, and 26 %, respectively) despite the increase in HR (108 ± 6 beats/min vs. 73 ± 2 beats/min, respectively). These abnormalities were corrected by acute administration of ivabradine (1 mg/kg, iv). Ivabradine still exerted these effects when HR was controlled at 150 beats/min by atrial pacing. Interestingly, LV relaxation filling, LV early filling and LV peak early filling were strongly correlated with both isovolumic contraction and relaxation. In conclusion, ivabradine improves LV filling during chronic hypertension. The mechanism involves LV contraction-relaxation coupling through normalization of isovolumic contraction and relaxation as well as HR-independent mechanisms.

Heterogeneity of apex-to-base dispersion in diastolic lengthening is related to impaired global left ventricular relaxation in patients with hypertrophic cardiomyopathy

BACKGROUND

The presence of apex-to-base disparity in diastolic left ventricle (LV) endocardial lengthening, based on an electromechanical activation sequence, has been recognized as an important determinant of LV diastolic properties. However, the behavior of LV apical and basal diastolic lengthening and its relationship to LV filling in hypertrophic cardiomyopathy (HCM) are unknown.

METHODS

We obtained basal and apical LV short-axis views in 27 patients with non-obstructive HCM and 25 healthy volunteers. The patients with HCM were subdivided into two groups; those with apical hypertrophy [APH(+)] or those without apical hypertrophy [APH(-)]. Eight equiangular points on the endo-myocardium at end diastole were placed in each view, and the movements of these points were automatically tracked using a two-dimensional echocardiographic tissue tracking system. Time-LV internal diameter curves were obtained and averaged. The time intervals from the aortic valve closure to the point of the first 40% of peak diastolic lengthening (T 40) were measured in each view. The standard deviation of the time to peak systolic circumferential shortening at the base and apex were calculated to assess the heterogeneity of LV contraction.

RESULTS

The time difference in the T 40 between the apex and base (dt-T 40) in the HCM-APH(+) and HCM-APH(-) groups was greater than that in the control group. The heterogeneities in LV apical systolic shortening in the HCM groups were greater than those in the control group. There were good linear correlations between the dt-T 40 and the LV early diastolic echo-parameters and the LV mass index.

CONCLUSIONS

Delayed apical relaxation and filling in patients with HCM is related to LV diastolic dysfunction and systolic dyssynchronous contraction.

Relationship Between Asynchronous Myocardial Contraction and Left Ventricular Systolic and Diastolic Function-Assessment Using the ECG-Gated Polar Map With 99mTc-Methoxy-Isobutyl Isonitrile-

BACKGROUND

To quantitate the degree of 3-dimensional asynchronous myocardial contraction, an ECG-gated polar map method was developed with (99m)Tc-methoxy-isobutyl isonitrile, and used to investigate the relationship between asynchrony and left ventricular (LV) function.

METHODS AND RESULTS

Twelve normal subjects and 38 patients with an old myocardial infarction were studied with ECG-gated single-photon emission computed tomography (SPECT). In each frame, a myocardial perfusion polar map was reconstructed and the peak contraction phase in each pixel was displayed (phase map). The degree of asynchronous contraction was assessed from the standard deviations of the peak contraction phase (SDP) on the phase map. Ejection fraction (EF), peak ejection rate (PER), 1/3EF, peak filling rate (PFR) and 1/3 filling fraction (1/3FF) were calculated by the quantitative gated SPECT software, and E/A from Doppler echocardiography. The SDP was compared with these parameters. Correlation coefficients and p values between the SDP and parameters of cardiac function were as follows: EF, r=-0.69 (p<0.001); PER, r=-0.54 (p<0.001); 1/3EF, r=-0.57 (p<0.001); PFR, r=-0.29 (p<0.05); 1/3FF, r=-0.63 (p<0.001); E/A, r=-0.11 (p=0.51).

CONCLUSIONS

There was a negative correlation between the SDP and LV systolic and diastolic function, which confirmed the functional significance of asynchrony on cardiac function.

Cardiovascular Circulation and Hepatic Perfusion of Pigs in 4-Dimensional Films Evaluated by 256-Slice Cone-Beam Computed Tomography

BACKGROUND

In both cardiac and hepatic disorders it is desirable to accurately visualize the direction and scale of blood flow in the whole organ in pulsating 3-dimensional (D) images, which are known as 4-D images.

METHODS AND RESULTS

The present study used 256-slice cone-beam computed tomography (CT) (Athena, Sony-Toshiba) at one rotation per second and a section thickness of 0.5 mm to show the dynamics of cardiovascular circulation and hepatic perfusion by contrast injection in 4-D films of pigs. Four pigs (20 kg each) were anesthetized with isoflurane. The distal tips of the catheters were positioned in the inferior vena cava (IVC) (pigs 1-3) and in the proper hepatic artery (pig 4). Volumetric scanning and injection of contrast material were started simultaneously and continued for 25 s with image reconstruction at 1-s intervals. In pigs 1-3, 4-D filming revealed the dynamics of cardiovascular circulation, first in the IVC, followed by the right ventricle and pulmonary artery, then the left ventricle, left atrium, pulmonary vein, and finally, the right heart disappeared and only the left heart and aorta remained visible. In pig 4, the hepatic arterial trees, followed by the venous trees, could be easily visualized in turn on the 4-D images.

CONCLUSIONS

This technology successfully demonstrated cardiovascular circulation and hepatic perfusion in 4-D and will have clinical applicability.

Effects of Postischemic Regional Left Ventricular Diastolic Wall Motion Abnormalities or Delayed Relaxation Following Coronary Vasospasm on Global Diastolic Function

BACKGROUND

Regional left ventricular (LV) diastolic wall motion abnormalities detected by color kinesis (CK), an echocardiographic technique, may be a more sensitive measure to postischemic damage following coronary spasm than parameters of global diastolic function.

METHODS AND RESULTS

Regional LV diastolic wall motion was evaluated by using CK in 18 patients with variant angina on the day following coronary spasm, which was induced by intracoronary acetylcholine. Fractional regional LV cavity area expansion in the short-axis view during the first 30% of the LV filling time, was used to identify postischemic asynchronous diastolic wall motion. Regional delayed relaxation was observed in any of the LV regions in all the patients, who were divided into 2 groups (Group S: 7 patients with single-vessel spasm with regional delayed relaxation in one area. Group M: 11 patients with multivessel spasm or spasm of the proximal left anterior descending branch with regional delayed relaxation in multiple areas). In Group S, no abnormality (0%) was noted in any of the indexes of global diastolic function including the isovolumic relaxation time, the ratio of peak rapid filling to peak atrial filling velocities and the deceleration time. In contrast, in 5 (45%) of the Group M patients, abnormalities were noted in all of those indexes.

CONCLUSIONS

Postischemic regional LV-delayed relaxation following coronary vasospasm was detected sensitively by analysis of CK images. The indexes of global LV diastolic function are insensitive to postischemic damage following single vessel spasm, although they are somewhat sensitive following multivessel spasm.

Acute Effects of Diltiazem on Regional Left Ventricular Diastolic Filling Dynamics in Patients With Hypertrophic Cardiomyopathy as Assessed by Color Kinesis

BACKGROUND

The effect of calcium antagonists on regional left ventricular (LV) filling dynamics in patients with hypertrophic cardiomyopathy (HCM) is not well known, so the present study evaluated the results of echocardiography with color kinesis (CK) analysis during diltiazem infusion.

METHODS AND RESULTS

Nineteen patients (16 men, 3 women; mean age 55+/-15 years) underwent echocardiography with CK analysis during intravenous diltiazem (10 mg/2 min). Using the quantitative CK software the LV short-axis image was divided into 6 segments and the percent endocardial expansion at the early, mid- and late-diastolic filling time was averaged for all segments, with the standard deviation of the mean used as an index of diastolic asynchrony (asynchrony index). The regional mean filling time was also measured for the corresponding segments. As global diastolic parameters, the global filling time, peak filling rate, and the time-to-peak filling were calculated. After the administration of diltiazem, the asynchrony index was decreased for all three diastolic filling times. Diltiazem shortened the mean filling time overall, especially in the posterior and lateral wall segments. These findings were associated with significant improvement in the CK-derived global diastolic parameters.

CONCLUSIONS

Diltiazam has a favorable effect on LV diastolic asynchrony, which may account for the acute changes in global LV relaxation.