Low-dose dobutamine induces left ventricular mechanical dyssynchrony in patients with dilated cardiomyopathy and a narrow QRS: A study using real-time three-dimensional echocardiography

Low-dose dobutamine stress gated blood pool SPECT assessment of left ventricular contractile reserve in ischemic cardiomyopathy: a feasibility study

PURPOSE

The purpose of the present study was to evaluate the feasibility of gated blood pool single-photon emission computed tomography (GBPS) with low-dose dobutamine (LDD) stress test, performed on a single-photon emission computed tomography (SPECT) camera equipped with cadmium-zinc-telluride (CZT) solid-state detectors, in assessing of left ventricle (LV) contractile reserve in patients with ischemic cardiomyopathy (ICM).

METHODS

A total of 52 patients (age 59 ± 7.2 years, 47 men and 5 women) with ICM and a control group of 10 patients without obstructive coronary artery lesion underwent GBPS and transthoracic echocardiography (TTE) at rest and during LDD stress test (5, 10, 15 µg/kg/min). The duration of each GBPS step was 5 min. Stress-induced changes in LV ejection fraction (ΔLVEF), peak ejection rate, LV volumes, and mechanical dyssynchrony (phase histogram standard deviation, phase histogram bandwidth and entropy) obtained with GBPS were estimated.

RESULTS

All GBPS indices except end-diastolic volume showed significant dynamics during stress test in both groups. The majority of parameters in ICM patients showed significant changes at a dobutamine dose of 10 µg/kg/min as compared to the rest study. Seventeen percent of ICM patients, but none from the control group, showed a decrease in LVEF during stress, accompanied by a significant increase in entropy. The intra- and inter-observer reproducibility was excellent for both rest and stress studies. There was a moderate correlation (r = 0.5, p = 0.01) between GBPS and TTE, with a mean difference value of - 1.7 (95% confidence interval - 9.8; 6.4; p = 0.06) in ΔLVEF.

CONCLUSION

Low-dose dobutamine stress GBPS performed with high-efficiency CZT-SPECT cameras can be performed for evaluating stress-induced changes in LV contractility and dyssynchrony with lower acquisition time. A dobutamine dose of 10 µg/kg/min can potentially suffice to detect stress-induced changes in patients with ICM during GBPS.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04508608 (August 7, 2020).

Comparison of the dyssynchrony parameters recorded with gated SPECT in ischemic cardiomyopathy according to their repeatability at rest and to their ability to detect a synchrony reserve under dobutamine infusion

BACKGROUND

This study aimed to determine whether the repeatability of dyssynchrony assessment using gated myocardial perfusion SPECT (GSPECT) allows the detection of synchrony reserve during low-dose dobutamine infusion.

METHODS AND RESULTS

Sixty-one patients with ischemic cardiomyopathy and LV ejection fraction < 50% were prospectively included in 10 centers. Each patient underwent two consecutive rest GSPECT with 99mTc-labeled tracer (either tetrofosmin or sestamibi) to assess the repeatability of LV function and dyssynchrony parameters, followed by a GSECT acquisition during low-dose dobutamine infusion. LV dyssynchrony was assessed using QGS software through histogram bandwidth (BW), standard deviation of the phase (SD), and entropy. Repeatability was assessed with Lin's concordance correlation coefficient (CCC). Entropy showed a higher CCC (0.80) compared to BW (0.68) and SD (0.75). On average, dobutamine infusion yielded to improve both BW (P = .049) and entropy (P = .04) although significant improvements, setting outside the 95% confidence interval of the repeatability analysis, were documented in only 6 and 4 patients for BW and entropy, respectively.

CONCLUSIONS

A synchrony reserve may be documented in patients with ischemic cardiomyopathy through the recording of BW and entropy with low-dose dobutamine GSPECT, with the additional advantage of a higher repeatability for entropy.

Phase analysis of gated blood pool SPECT for multiple stress testing assessments of ventricular mechanical dyssynchrony in a tachycardia-induced dilated cardiomyopathy canine model

BACKGROUND

Stress-induced dyssynchrony has been shown to be independently correlated with clinical outcomes in patients with dilated cardiomyopathy (DCM) and narrow QRS complexes. However, the extent to which stress levels affect inter- and intraventricular dyssynchrony parameters remains unknown.

METHODS

Ten large dogs were submitted to tachycardia-induced DCM by pacing the right ventricular apex for 3-4 weeks to reach a target ejection fraction (EF) of 35% or less. Stress was then induced in DCM dogs by administering intravenous dobutamine up to a maximum of 20 μg·kg-1·min-1. Hemodynamic and ventricular dyssynchrony data were analyzed by left ventricular (LV) pressure measurements and gated blood pool SPECT (GBPS) imaging. In order to assess mechanical dyssynchrony in DCM subjects and compare it with that of 8 normal counterparts, we extracted the following data: count-based indices of LV contraction homogeneity index (CHI), entropy and phase standard deviation, and interventricular dyssynchrony index.

RESULTS

A significant LV intraventricular dyssynchrony (CHI: 96.4 ± 1.3% in control vs 78.6% ± 10.9% in DCM subjects) resulted in an intense LV dysfunction in DCM subjects (EF: 49.5% ± 8.4% in control vs 22.6% ± 6.0% in DCM), compared to control subjects. However, interventricular dyssynchrony did not vary significantly between the two groups. Under stress, DCM subjects showed a significant improvement in ventricular functional parameters at each level (EF: 22.6% ± 6.0% at rest vs 48.1% ± 5.8% at maximum stress). All intraventricular dyssynchrony indices showed a significant increase in magnitude of synchrony from baseline to stress levels of greater than or equal to 5 μg·kg-1·min-1 dobutamine. There were individual differences in the magnitude and pattern of change in interventricular dyssynchrony during the various levels of stress.

CONCLUSIONS

Based on GBPS analyses, different levels of functional stress, even in close intervals, can have a significant impact on hemodynamic and intraventricular dyssynchrony parameters in a DCM model with narrow QRS complex.

Left Ventricular Dyssynchrony by Three-Dimensional Echocardiography: Current Understanding and Potential Future Clinical Applications

Left ventricular mechanical dyssynchrony is an important prognostic factor for patients with symptomatic systolic heart failure and has emerged as a therapeutic target for cardiac resynchronization therapy (CRT). However, approximately one-third of patients fail to improve after CRT based on current guideline recommendations and electrocardiographic criteria. Two-dimensional echocardiography and tissue Doppler-based techniques have shown variable results in assessment of left ventricular (LV) dyssynchrony and have limited value in clinical practice. Three-dimensional echocardiography (3DE) is an appealing novel imaging modality that has been recently used in quantitative evaluation of global and regional LV function. There is accumulating evidence that 3DE measurement of LV systolic dyssynchrony index may potentially play a role in predicting the short- and long-term response to CRT and further improve patient selection for CRT. New developments in 3DE speckle tracking technique and strain analysis may further improve the accuracy of LV mechanical dyssynchrony assessment in this population. In addition, recent studies suggest that mechanical dyssynchrony is present in patients with LV hypertrophy and diastolic heart failure. Three-dimensional echocardiographic assessment of dyssynchrony may aid in diagnosis and in predicting long-term outcome in these patients. We will summarize current understanding of 3DE techniques and parameters in assessment of LV mechanical dyssynchrony in the population of patients with systolic heart failure, LV hypertrophy, and diastolic heart failure. A number of the novel 3DE techniques described in this review are early in their stage of development, and they will continue to evolve and need further testing in large multicenter studies.