Influence of temporal smoothing on quantitation of left ventricular function by gated blood pool scintigraphy

Ventricular mechanical dyssynchrony and resynchronization therapy in heart failure: a new indication for Fourier analysis of gated blood-pool radionuclide ventriculography

In patients with decreased left ventricular ejection fraction and conduction disease, ventricular mechanical dyssynchrony has been demonstrated. To date, resynchronization by biventricular pacing is increasingly used since it improves ventricular function and exercise capacity in patients with heart failure. To optimize and evaluate the effect of resynchronization therapy and to identify patients who may benefit from biventricular pacing the assessment of left ventricular synchronicity is essential. Therefore, a non-invasive and reproducible technique to obtain information on ventricular synchrony is clinically valuable. In this review, the technical background and the role of phase analysis of gated blood-pool nuclear ventriculography in the assessment of ventricular mechanical synchrony, especially in heart failure patients subjected to biventricular pacing, will be discussed.

Accurate estimation of global and regional cardiac function by retrospectively gated multidetector row computed tomography

Retrospective reconstruction of ECG-gated images at different parts of the cardiac cycle allows the assessment of cardiac function by multi-detector row CT (MDCT) at the time of non-invasive coronary imaging. We compared the accuracy of such measurements by MDCT to cine magnetic resonance (MR). Forty patients underwent the assessment of global and regional cardiac function by 16-slice MDCT and cine MR. Left ventricular (LV) end-diastolic and end-systolic volumes estimated by MDCT (134+/-51 and 67+/-56 ml) were similar to those by MR (137+/-57 and 70+/-60 ml, respectively; both P=NS) and strongly correlated (r=0.92 and r=0.95, respectively; both P<0.001). Consequently, LV ejection fractions by MDCT and MR were also similar (55+/-21 vs. 56+/-21%; P=NS) and highly correlated (r=0.95; P<0.001). Regional end-diastolic and end-systolic wall thicknesses by MDCT were highly correlated (r=0.84 and r=0.92, respectively; both P<0.001), but significantly lower than by MR (8.3+/-1.8 vs. 8.8+/-1.9 mm and 12.7+/-3.4 vs. 13.3+/-3.5 mm, respectively; both P<0.001). Values of regional wall thickening by MDCT and MR were similar (54+/-30 vs. 51+/-31%; P=NS) and also correlated well (r=0.91; P<0.001). Retrospectively gated MDCT can accurately estimate LV volumes, EF and regional LV wall thickening compared to cine MR.

Evaluation of coronary artery bypass grafts by magnetic resonance imaging

Magnetic resonance (MR) angiography and flow mapping have the potential to become a major noninvasive diagnostic tool for the assessment of coronary artery bypass graft morphology and function. Several MR sequences, such as conventional non-respiratory compensated methods, and phase contrast cine flow sequences have been reported for the evaluation of bypass graft patency. However the visualization of different graft segments and the detection of graft stenosis remains difficult. Recent advances in MR coronary angiography and flow mapping are volume coronary angiongraphy with targeted scans, navigator gated angiography, contrast-enhanced angiography, and breath-hold or navigator gated flow sequences. Future approaches, such as navigator gated fast MR techniques resulting in high-resolution angiography in combination with breath-hold MR flow mapping with high temporal resolution, might allow a comprehensive evaluation of bypass graft stenosis and function. This review article will address the major issues concerning the MR evaluation of bypass grafts.

Echo planar MRI of the heart on a standard system: validation of measurements of left ventricular function and mass

OBJECTIVE

Our goal was to validate cardiac measurements derived from multishot echo planar MRI (EPI) as compared with the well validated conventional GRE technique.

METHOD

Ten healthy subjects underwent breath-hold EPI and non-breath-hold GRE imaging in the short axis orientation of the left ventricle (LV) on a standard 1.5 T MR system. Ten section levels were obtained to encompass the entire LV. Measurements were obtained of end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), LV mass, time to end-systole (TES), and peak filling rate (PFR). Analysis of variance was performed to determine agreement between GRE- and EPI-derived measurements.

RESULTS

The acquisition time for EPI was much shorter than that for GRE (2.5 vs. 15 min). Both imaging techniques yielded good quality images allowing LV volumetrics. Agreement between GRE and EPI was best for measurements of EDV, SV, and LV mass; somewhat less agreement was found for ESV, EF, TES, and PFR. The intraobserver variability for measuring TES and PFR was higher for GRE than EPI (one sided F test; critical values at p = 0.05 were > 3.18).

CONCLUSION

Multishot EPI of the heart provides accurate measurements of LV function and mass in a time-efficient manner.

Effect of mibefradil on left ventricular diastolic function in patients with congestive heart failure

Calcium antagonists have antihypertensive and antianginal properties. In heart failure, however, their use can be hazardous, as systolic function can deteriorate. This may not be true of the new calcium antagonist mibefradil, which has a new chemical structure. Calcium antagonists may also be beneficial for diastolic left ventricular function in coronary artery disease. To investigate the possible effects of mibefradil on diastolic left ventricular function, we performed the present study as a multicenter, double-blind,placebo-controlled, multiple-dose safety trial. Fifteen patients with New York Heart Association (NYHA) class II or III for dyspnea and depressed ejection fraction (<40%) due to a previous myocardial infarction were investigated. The measured nuclear angiographic parameters included ejection fraction (EF), peak ejection rate (PER), and peak filling rate (PFR). Systolic and diastolic blood pressure (SBP, DBP) and heart rate (HR) were also obtained. Group I (5 patients) received placebo medication; group IIA (6 patients) received mibefradil 6.25, 12.5, or 25 mg/day; and group IIB (4 patients) received mibefradil 50 or 100 mg/day. Measurements were made before and after the first dose and after 1 week of treatment before and after the final dose. Mibefradil clearly decreased HR (repeated-measures analysis of variance p < 0.05). No statistically significant effects of mibefradil were noted on SBP or DBP or on systolic and diastolic left ventricular function. In our study conditions, mibefradil caused no worsening of systolic function and preserved diastolic function in short-term treatment of patients with decreased EF and heart failure.

Assessment of left ventricular diastolic function in dilated cardiomyopathy with cine magnetic resonance imaging: effect of an angiotensin converting enzyme inhibitor, benazepril

The effects of angiotensin converting-enzyme inhibitor, benazepril, on diastolic function in patients with dilated cardiomyopathy, with (n = 4) or without (n = 11) mitral regurgitation, were examined with the time-volume curve of the left ventricle derived from cine magnetic resonance images. Peak filling rate/end-systolic volume and ejection fraction were increased in the group without regurgitation (p < 0.01) but not in the group with regurgitation after treatment. There was a strong correlation between peak filling rate/end-systolic volume and ejection fraction (r = 0.89) and between the change in peak filling rate/end-systolic volume and that in ejection fraction after treatment (r = 0.74) in the group without regurgitation. These findings suggest that in some patients with dilated cardiomyopathy benazepril has favorable effects on diastolic function, which seem to be related to improvement in systolic function. This drug may not be as beneficial in patients with dilated cardiomyopathy complicated by mitral regurgitation.

Quantitative dynamics of left ventricular emptying and filling as a function of heart size and stroke volume in pure aortic regurgitation and in normal subjects

Quantitative understanding of the dynamics of left ventricular (LV) emptying and filling as the left ventricle dilates but maintains ejection fraction is limited. Cine computed tomography was used to quantify peak LV emptying and filling characteristics in 30 patients with normal ejection fraction but variable end-diastolic and stroke volumes. Group I consisted of 15 normal male patients and group II of 15 male patients with chronic, well-compensated, isolated aortic regurgitation. For each patient global LV volumes, absolute peak emptying and peak early diastolic filling rates and the timing of these maximal slopes were quantified. Mean arterial pressure and heart rate were within the normal range and ejection fraction and ages similar between groups I and II. Between-group analyses showed significantly increased end-diastolic and stroke volumes in group II compared with group I but nearly identical end-systolic volumes. Likewise, absolute peak emptying and filling rates were significantly greater in group II than in group I patients. The ratio of peak emptying rate to peak filling rate remained constant between groups. Timing of peak emptying and filling were similar in both groups. Absolute LV peak emptying and filling rates were found to vary linearly with end-diastolic and stroke volumes in all subjects examined. However, referencing peak emptying or peak filling rates to end-diastolic or total stroke volumes eliminated intergroup differences. Thus, in the presence of preserved ejection fraction and normal arterial pressure, the dynamic rates of LV emptying and early diastolic filling increase in direct proportion to absolute end-diastolic and stroke volumes, but the ratio of peak emptying to peak filling rate remains constant.