The role of short- and long-axis function in determining late diastolic left ventricular filling in patients with hypertension: assessment by pulsed Doppler tissue imaging

Short-axis epicardial volume change is a measure of cardiac left ventricular short-axis function, which is independent of myocardial wall thickness

Fractional shortening (FS) by echocardiography is considered to represent the short-axis contribution to the stroke volume (SV), also called short-axis function. However, FS is mathematically coupled to the amount of myocardium, since it rearranges during atrioventricular plane displacement (AVPD). The SV is the sum of the volumes generated by 1) reduction in outer volume of the heart, and 2) inner AVPD. The long-axis contribution to the SV is generated by AVPD, and thus the short-axis contribution is the remaining outer volume change of the heart, which should be unrelated to myocardial wall thickness. We hypothesized that both endocardial and midwall shortening indexed to SV are dependent on myocardial wall thickness, whereas epicardial volume change (EVC) indexed to SV is not. Twelve healthy volunteers (normals), 12 athletes, and 12 patients with dilated cardiomyopathy (ejection fraction < 30%) underwent cine cardiac magnetic resonance imaging. Left ventricular long-axis function was measured as the portion of the SV, in milliliters, generated by AVPD. EVC was defined as SV minus long-axis function. Endocardial and midwall shortening were measured in a midventricular short-axis slice. Endocardial shortening/SV and midwall shortening/SV both varied in relation to end-diastolic myocardial wall thickness (R(2) = 0.16, P = 0.008 and R(2) = 0.14, P = 0.012, respectively), whereas EVC/SV did not (R(2) = 0.00, P = 0.37). FS is dependent on myocardial wall thickness, whereas EVC is not and therefore represents true short-axis function. This is not surprising considering that FS is mainly caused by rearrangement of myocardium secondary to long-axis function. FS is therefore not synonymous with short-axis function.

Systo-diastolic ventricular function in patients with hypertension: an echocardiographic tissue doppler imaging evaluation study

BACKGROUND

Tissue Doppler imaging (TDI) has evolved to become a useful non invasive method that can complement other echocardiographic techniques in the assessment of left ventricular function in different clinical conditions. Spectral pulsed TDI can provide measurements of regional systolic and diastolic myocardial velocities and is particularly useful in detecting abnormalities of left ventricular systolic and diastolic function. We investigated the presence of systo-diastolic dysfunction in patients (pts) with hypertension compared with pts affected by hypertensive cardiomyopathy and normal control subjects.

METHODS

We evaluated 214 pts with traditional echocardiography and TDI: 69 normal control subjects (Group A); 145 pts with hypertension, divided according to base echocardiographic evaluation in 74 with no evidence of hypertensive cardiomyopathy (diastolic dysfunction and ventricular hypertrophy, Group B), and 71 with evidence of hypertensive cardiomyopathy (Group C). Pts groups were matched for age, sex, heart rate, smoking status and body surface area.

RESULTS

There were no significant differences in ventricular diameters, volumes, shortening and ejection fraction values; TDI showed a progressive systolic wave peak reduction from Group A to B and from Group B to C. Routinely Doppler diastolic function did not show any significant difference between Group A and B; TDI showed progressive E wave peak velocity decrease and A wave peak velocity increase from Group A to B and C and from Group B to C.

CONCLUSIONS

TDI evaluation showed a ventricular systolic dysfunction in pts with hypertensive cardiomyopathy; in addition, an early mild systo-diastolic dysfunction was detected in subjects with hypertension but no evidence of hypertensive cardiomyopathy.

Regional differences in spontaneous Ca2+ spark activity and regulation in cat atrial myocytes

Calcium sparks result from the concerted opening of a small number of Ca2+ release channels (ryanodine receptors, RyRs) organized in clusters in the membrane of the sarcoplasmic reticulum (SR). Calcium sparks represent the elementary events of SR Ca2+ release in cardiac myocytes, and their spatial and temporal summation results in whole-cell [Ca2+]i transients observed during excitation-contraction coupling (ECC). Atrial myocytes generally lack transverse tubules; however, during ECC Ca2+ release is initiated from junctional SR (j-SR) in the cell periphery from where activation propagates inwardly through Ca(2+)-induced Ca2+ release (CICR) from non-junctional SR (nj-SR). Despite the structural differences in the microdomains of RyRs of j-SR and nj-SR, spontaneous Ca2+ sparks are observed from both types of SR, albeit at different frequencies. In cells that showed spontaneous Ca2+ sparks from j-SR and nj-SR, subsarcolemmal (SS) Ca2+ sparks from the j-SR were 3-4 times more frequent than central (CTR) Ca2+ sparks occurring from nj-SR. Subsarcolemmal Ca2+ sparks had a slightly higher amplitude, but were essentially identical in their spatial spread and duration when compared to CTR Ca2+ sparks. Sensitization of RyRs with a low concentration (0.1 mM) of caffeine led to a 107% increase in the frequency of CTR Ca2+ sparks, whereas the SS Ca2+ spark frequency increased by only 58%, suggesting that the nj-SR is capable of much higher Ca2+ spark activity than observed normally in unstimulated cells. The L-type Ca2+ channel blocker verapamil reduced SS Ca2+ spark frequency to 38% of control values, whereas Ca2+ spark activity from nj-SR was reduced by only 19%, suggesting that SS Ca2+ sparks are under the control of Ca2+ influx from the extracellular space. Removal of extracellular Ca2+ eliminated SS Ca2+ sparks completely, whereas Ca2+ sparks from the nj-SR continued, albeit at a lower frequency. In membrane-permeabilized (saponin-treated) atrial myocytes, where [Ca2+] can be experimentally controlled throughout the entire myocyte, j-SR and nj-SR Ca2+ spark frequencies were identical, and Ca2+ sparks could be observed spaced at sarcomeric distances throughout the entire cell, suggesting that all release sites of the nj-SR can become active. Measurement of SR Ca2+ load (10 mM caffeine) revealed no difference between j-SR and nj-SR. The data suggest that in atrial myocytes, which lack a t-tubular system, the nj-SR is fully equipped with a three-dimensional array of functional SR Ca2+ release sites; however, in intact cells under resting conditions, peripheral RyR clusters have a higher probability of activation owing to their association with surface membrane Ca2+ channels, leading to higher spontaneous Ca2+ spark activity. In conclusion, Ca2+ sparks originating from both j-SR and nj-SR are rather stereotypical and show little differences in their spatiotemporal properties. In intact cells, however, the higher frequency of spontaneous SS Ca2+ sparks arises from the structural arrangement of sarcolemma and j-SR membrane and thus from the difference in the trigger mechanism.

Strain and strain rate imaging: a new clinical approach to quantifying regional myocardial function

On the basis of color Doppler myocardial motion data, 1-dimensional regional natural strain rate and strain curves can now be calculated by comparing local myocardial velocity profiles. Such deformation data sets may be an important, new, and more sensitive approach to quantifying both regional radial and long-axis function of the left or right ventricle in both acquired and congenital heart disease. The normal ranges of regional velocity, strain rate, and strain values have already been determined in both adults and children. This review will focus both on the potential clinical applications of these new ultrasound-based deformation parameters and the current limitations inherent in implementing the technique in everyday practice.

Noninvasive assessment of hemodynamic parameters in experimental stenosis of the ascending aorta

We sought to noninvasively evaluate left ventricular (LV) function after cardiac hypertrophy induced by experimental stenosis of the ascending aorta. Male Wistar rats (70-90 g) underwent ascending aorta constriction by the surgical placement of a titanium clip (n=5) or sham operation (n=6). High-resolution bidimensional, pulsed-wave Doppler (PWD) and pulsed-wave tissue Doppler imaging (TDI) were performed 22 weeks after surgery. PWD was used to obtain mitral flow velocities, and TDI was used to obtain velocities along the septal mitral annulus and LV posterior wall. Clip placement produced myocardial hypertrophy with decreased systolic myocardial peak velocity in both the long and short axes. Increased myocardial mass, that is, posterior wall and septal thickness, was indicative of ventricular remodeling. Diastolic dysfunction was observed, with an increased early to late ratio of mitral velocities and increased left atrium dimension, consistent with a left ventricular restrictive filling pattern.

Prognostic value of the atrial systolic mitral annular motion velocity in patients with left ventricular systolic dysfunction

BACKGROUND

Transmitral flow velocity variables are powerful predictors of poor prognosis in patients with left ventricular (LV) systolic dysfunction. However, these variables may not accurately reflect the severity of pulmonary congestion. This study was designed to determine whether the peak atrial systolic mitral annular motion velocity (MA-Aw) measured by pulsed Doppler tissue imaging can predict cardiac death or hospitalization for worsening heart failure in patients with LV systolic dysfunction.

METHODS

MA-Aw was recorded in 96 patients with LV systolic dysfunction who were followed up for 29 +/- 10 months. All patients underwent Doppler echocardiography on entry into the study, and cardiac catheterization was performed in 45 patients. Patients were divided into 3 groups on the basis of the ratio of early (E) to late (A) diastolic filling (E/A) of the transmitral flow velocity: group 1 (n=31; E/A < 1); group 2 (n=37; 1 < or = E/A < 2); and group 3 (n=28; E/A > or = 2).

RESULTS

During follow-up, 36 patients (38%) died of cardiac causes and 34 (35%) were hospitalized for worsening heart failure. There were 2 cardiac deaths (6%) in group 1, 14 (39%) in group 2, and 20 (56%) in group 3. The MA-Aw correlated closely with the mean pulmonary capillary wedge pressure. Univariate Cox model analysis showed that MA-Aw < or = 5 cm/s was the most powerful predictor of cardiac death or hospitalization for worsening heart failure compared with clinical, hemodynamic, and the other echocardiographic variables. Furthermore, MA-Aw < or = 5 cm/s was clearly discernible as a good predictor of cardiac mortality on multivariate Cox model and as assessed by Kaplan-Meier method.

CONCLUSION

The MA-Aw obtained by pulsed Doppler tissue imaging is a sensitive index of pulmonary congestion in patients with LV systolic dysfunction. It is a simple and noninvasive outcome measure and can be used to monitor treatment.