Intraventricular Pressure Gradients in Left Ventricular Aneurysms Determined by Color M-Mode Doppler Method: An Animal Study

Non-Invasive Assessment of the Intraventricular Pressure Using Novel Color M-Mode Echocardiography in Animal Studies: Current Status and Future Perspectives in Veterinary Medicine

The assessment of diastolic function has received great interest in order to comprehend its crucial role in the pathophysiology of heart failure and for the early identification of cardiac events. Silent changes in the intraventricular flow (IVF) dynamics occur before the deterioration of the cardiac wall, although they cannot be detected using conventional echocardiography. Collective information on left ventricular (LV) pressures throughout the cardiac cycle has great value when dealing with patients with altered hemodynamics. Accurate pressure measurement inside the ventricle can be obtained by invasive methods to determine the LV diastolic pressures, which reflect the myocardial relaxation and compliance. However, catheterization is only feasible in the laboratory setting and is not suitable for clinical use due to its disadvantages. In contrast, echocardiography is simple, safe, and accessible. Color M-mode echocardiography (CMME) is an advanced cardiac evaluation technique that can measure the intraventricular pressure differences (IVPDs) and intraventricular pressure gradients (IVPGs) based on the Doppler shift of the IVF. Recently, the assessment of IVPD and IVPG has gained growing interest in the cardiovascular literature in both animal and human studies as a non-invasive method for the early diagnosis of cardiac dysfunctions, especially diastolic ones. The usability of IVPD and IVPG has been reported in various surgically induced heart failure or pharmacologically altered cardiac functions in rats, dogs, cats, and goats. This report aims to give an overview of the current studies of CMME-derived IVPD and IVPG in animal studies and its feasibility for clinical application in veterinary practice and to provide the prospects of the technique's ability to improve our understanding.

Effects of Individual and Coexisting Diabetes and Cardiomyopathy on Diastolic Function in Rats (Rattus norvegicus domestica)

The goal of this study was to evaluate diastolic intraventricular pressure gradients (IVPG) and 2-dimensional tissue tracking (2DTT) patterns during diabetes and cardiomyopathy. Rats (n = 60) were induced to become diabetic (DM group, n = 15) by using streptozotocin, to become cardiomyopathic (CM group, n = 15) by using isoproterenol, and to become both diabetic and cardiomyopathic (DMCM group, n = 15); control rats (CT group, n = 15) were injected with saline. Two months after induction, all rats underwent conventional echocardiography, IVPG, and 2DTT and then were euthanized for microscopic examination of cardiac fibrosis. Compared with the controls, all 3 treated groups showed diastolic dysfunction and delayed cardiac relaxation. DMCM rats showed the most pronounced cardiac abnormalities. In addition, CM and DMCM groups had showed decreased middle IVPG, whereas DMCM rats had decreased midapical IVPG. Although the overall IVPG of the CM group was normal, the middle segment was significantly decreased. 2DTT results showed that the DMCM group had a delay in relaxation compared with other groups. IVPG and 2DTT can be used to overcome the limitation of conventional echocardiographic methods and reveal diastolic dysfunction. DM worsened diastolic function during cardiac disease.

Assessment of left ventricular diastolic dysfunction based on the intraventricular velocity difference by vector flow mapping

OBJECTIVES

The diastolic intraventricular velocity difference represents diastolic function of the left ventricle (LV). Here we analyzed the LV diastolic intraventricular velocity difference in patients with impaired LV function based on the ventricular flow rate profile by vector flow mapping.

METHODS

Patients with LV diastolic dysfunction were divided into 2 groups: chronic heart failure with restricted filling (group 1; n = 27) and hypertension with abnormal relaxation (group 2; n = 34). Healthy participants were identified as controls (group 3; n = 22). Left ventricular inflow color Doppler findings were analyzed by the vector profile model with the vector flow mapping technology offline. The flow velocity rates at the base and apex of the LV were measured from vector profiles with the vector flow mapping technology. The diastolic intraventricular velocity difference was calculated from flow velocity rates.

RESULTS

The diastolic intraventricular velocity difference calculated from vector flow mapping was significantly lower in both groups with LV diastolic dysfunction than the control group (mean ± SD, 79.95 ± 9.88 cm/s in controls versus 40.35 ± 6.80 cm/s in group 1 and 48.50 ± 6.03 cm/s in group 2; P < .001 for both). The diastolic intraventricular velocity difference had a significant association with the ejection fraction (P = .0002) and deceleration time (P = .0306). The peak atrial contraction velocity was negatively related to the diastolic intraventricular velocity difference (P = .0003).

CONCLUSIONS

The diastolic intraventricular velocity difference derived from the LV velocity rate by the vector profile model on vector flow mapping can be potentially used for quantitative assessment of LV diastolic function. Vector flow mapping proved to be clinically practical for reflecting LV diastolic dysfunction in pathologic states.

Non-invasive assessment of left ventricular relaxation during atrial fibrillation using mitral flow propagation velocity

AIMS

To elucidate the usefulness of the early diastolic mitral flow propagation velocity (V(p)) obtained from colour M-mode Doppler for non-invasively assessing left-ventricular (LV) relaxation during atrial fibrillation (AF).

METHODS AND RESULTS

Ten healthy adult dogs were studied to correlate V(p) with the invasive minimum value of the first derivative of LV pressure decay (dP/dt(min)) and the time constant of isovolumic LV pressure decay (tau) at baseline, during rapid and slow AF, and during AF after inducing myocardial infarction. There were significant positive and negative curvilinear relationships between V(p) and dP/dt(min) and tau, respectively, during rapid AF. After slowing the ventricular rate, the average value of V(p) increased, while dP/dt(min) increased and tau decreased. After inducing myocardial infarction, the average value of V(p) decreased, while dP/dt(min) decreased and tau increased.

CONCLUSION

The non-invasively obtained V(p) evaluates LV relaxation even during AF regardless of ventricular rhythm or the presence of pathological changes.