Analysis of phase-angle histograms from equilibrium radionuclide studies: correlation with semiquantitative grading of wall motion

Equilibrium radionuclide angiography compared with tissue doppler imaging for detection of right ventricular dyssynchrony and prediction of acute response to cardiac resynchronization therapy

OBJECTIVE

The aim of this study was to compare tissue doppler imaging (TDI) and equilibrium radionuclide angiography (ERNA) for detection of right ventricular (RV) dyssynchrony and prediction of the acute response to cardiac resynchronization therapy (CRT).

METHODS

This study was approved by the local ethics committee of Huai'an First People's Hospital. Patient consent was not provided due to the use of completely anonymous images from which the individual could not be identified in this study. Thirty-three patients with nonischemic dilated cardiomyopathy underwent both TDI and ERNA before and within 48 hour after CRT implantation. RV dyssynchrony was measured with TDI using the difference in time to peak systolic velocity between the RV free wall and ventricular septum (RV-T). With ERNA, the standard of RV mean phase angle and RV phase standard deviation (RVmPA% and RVPSD%) were assessed.

RESULTS

Moderate positive correlations were observed among baseline RVmPA%, RVPSD% and RV-T (r = 0.689 and 0.716, P < .001). Twenty patients (61%) with a reduction of at least 15% in LV end-systolic volume were categorized as acute responders after CRT. Responders showed significant reduction in RVmPA% and RVPSD% after CRT (53.60 ± 4.15% to 43.95 ± 6.88% and 14.00 ± 2.41% to 10.40 ± 1.67%, P < .05), whereas RV-T remained unchanged (50.10 ± 10.28 ms to 49.25 ± 13.64ms, NS). Receiver operating characteristic curve showed that the cut-off value of RV-T was 48.5ms, yielding 65% sensitivity and 77% specificity to predict acute respond to CRT. The cut-off value of RVmPA% was 49.5%, yielding 85% sensitivity and 85% specificity and the cut-off value of RVPSD% was 11.5%, yielding 85% sensitivity and 92% specificity.

CONCLUSION

ERNA might be an appropriate alternative to TDI for assessment of RV dyssynchrony. Either RVmPA% or RVPSD% was highly predictive for acute response to CRT.

Quantitative assessment of cardiac mechanical synchrony using equilibrium radionuclide angiography

BACKGROUND

Data on normal parameters of cardiac mechanical synchrony is limited, variable and obtained from small cohorts till date. In most studies, software used for such assessment has not been mentioned. The aim of study is to establish normal values of mechanical synchrony with equilibrium radionuclide angiography (ERNA) in a larger population using commercially available software.

METHODS

We retrospectively analysed ERNA studies of 108 patients having low pretest likelihood of coronary artery disease, no known history of cardiac disease, normal electrocardiogram and whose ERNA studies were considered normal by experienced observers. In addition, ten patients diagnosed with dilated cardiomyopathy (DCM) and having LVEF ≤ 40% underwent ERNA. Fourier first harmonic analysis of phase images was used to quantify synchrony parameters using commercially available software (XT-ERNA). Intraventricular synchrony for each ventricle was measured as the standard deviation of the LV and RV mean phase angles (SD LVmPA and SD RVmPA, respectively). Interventricular synchrony was measured as LV-RVmPA. Absolute interventricular delay was calculated as absolute difference between LV and RVmPA (without considering ± sign). All variables were expressed in milliseconds (ms) and degree (°). Intra-observer and inter-observer variabilities were assessed. Cut-off values for parameters were calculated from the normal database, and validated against patient group.

RESULTS

On phase analysis, LVmPA was observed to be 343 ± 48.5 milliseconds (174.7° ± 18.5°), SD LVmPA was 16.3 ± 5.4 milliseconds (8.2° ± 2.5°), RVmPA was 339 ± 50.4 milliseconds (171.8° ± 18.5°) and SD RVmPA was 37.3 ± 15.7 milliseconds (18.7° ± 7.2°). LV-RVmPA was observed to be 3.9 ± 21.7 milliseconds (2.9° ± 9.6°) and absolute interventricular delay was 16.3 ± 14.8 milliseconds (7.9° ± 6.1°). The cut-off values for the presence of dyssynchrony were estimated as SD LVmPA > 27.1 milliseconds (>13.2°), SD RVmPA > 68.7 milliseconds (>33.1°) and LV-RVmPA > 47.3 milliseconds (>22.1°). There was no statistically significant intra-observer or inter-observer variability. Using these cut offs, 9 patients with DCM showed the presence of left intraventricular dyssynchrony, 5 had right intraventricular dyssynchrony and 2 had interventricular dyssynchrony.

CONCLUSIONS

ERNA phase analysis offers an objective and reproducible tool to quantify cardiac mechanical synchrony using commercially available software and can be used in routine clinical practice to assess mechanical dyssynchrony.

Comparison of left ventricular contraction homogeneity index using SPECT gated blood pool imaging and planar phase analysis

BACKGROUND

There is growing interest in developing a practical technique to accurately assess ventricular synchrony. We describe a novel 3-dimensional (3D) gated blood pool single photon emission computed tomography (SPECT) approach, from which a contraction homogeneity index (CHI) is derived and compared with planar phase analyses.

METHODS AND RESULTS

Subjects underwent planar and SPECT blood pool acquisition. Planar images were processed for left ventricular ejection fraction computation and phase values. SPECT images were processed by our novel algorithm, with which CHI was computed. Overall, 235 patients (79% male; mean age, 62 +/- 11 years) completed the study. Left ventricular ejection fractions were similar by planar (33.5% +/- 13.5%) and 3D (34.7% +/- 12.7%) methods (r = 0.83, P < .0001). Mean phase angles for planar and tomographic methods were 126.3 degrees +/- 29.6 degrees and 124.4 degrees +/- 28.7 degrees , respectively (r = 0.53, P < .0001). Phase and amplitude signals were incorporated in the CHI, which was non-normally distributed with a median of 73.8% (interquartile range, 58.7%-84.9%). This index minimized the negative impact of dyskinetic wall segments with limited regional motion. The planar heterogeneity index (SDPhi) was 28.2 degrees (interquartile range, 17.5 degrees -46.8 degrees ) and correlated inversely with CHI (r = -0.61, P < .0001).

CONCLUSION

The novel 3D dispersion index CHI accounts for both phase delay of a dyssynchronous segment and its magnitude of contraction and is moderately correlated with planar phase analyses. Its potential in cardiac resynchronization therapy remains to be exploited.

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.

Echocardiographic quantification of left ventricular asynergy in coronary artery disease with Fourier phase imaging

BACKGROUND

Visual evaluation of wall motion is subjective and may be difficult in patients with impaired left ventricular function. Current algorithms used to analyze wall motion usually neglect motion asynchrony that may be profoundly altered in coronary artery disease. This study was to investigate whether the extent of left ventricular asynergy can be used to quantify the severity of regional myocardial dysfunction by the use of Fourier phase imaging.

METHODS

Echocardiographic cine loops of 21 patients with ischemic cardiomyopathy (EF < or = 40%) were mathematically transformed using a first-harmonic Fourier algorithm displaying the sequence of wall motion as phase angles in parametric images and regional phase histograms. Segmental fractional area shortening (FAC) and qualitative assessment of regional wall motion based on visual inspection served as reference method.

RESULTS

There was an inverse linear relationship between FAC and phase angles (r = -0.75, p < 0.01). Normal endocardial motion yielded low phase angles (mean 16 +/- 15 degrees SD). With an increase in wall motion abnormalities, phase angles were progressively delayed by 56 +/- 38 degrees in hypokinetic, by 88 +/- 38 degrees in akinetic, and by 143 +/- 33 degrees (p < 0.001) in dyskinetic segments.

CONCLUSIONS

These results demonstrate that left ventricular asynchrony is an indicator of regional myocardial dysfunction in coronary artery disease. Echocardiographic Fourier phase imaging can be used to quantify wall motion displaying contraction sequence in a simple and objective format.

Echocardiographic Fourier phase and amplitude imaging for quantification of ischemic regional wall asynergy: an experimental study using coronary microembolization in dogs

OBJECTIVES

This study investigated whether echocardiographic Fourier phase and amplitude imaging can be used to evaluate ischemia-related regional wall asynergy.

BACKGROUND

Because myocardial ischemia delays the onset and peak of endocardial inward motion and reduces its magnitude, Fourier phase and amplitude analysis of two-dimensional echocardiograms may be used to evaluate regional wall motion abnormalities objectively by analyzing temporal sequence and magnitude of endocardial motion.

METHODS

Digital cine loops of left ventricular long- and short-axis views were obtained in six anesthetized dogs at baseline and 1 to 30 min after coronary microembolization and were mathematically transformed using a first-harmonic Fourier algorithm to obtain phase angles and amplitudes of endocardial segments. Mean phase angles and amplitudes were compared with visual wall motion analysis based on a scoring system and quantitative analysis based on segmental fractional area shortening derived from planimetry.

RESULTS

Microembolization delayed segmental phase angles by 47 +/- 44 degrees in mild to moderate hypokinesia (fractional shortening [mean +/- SD] 41 +/- 13%) and by 77 +/- 63 degrees in severe hypokinesia (fractional shortening 13 +/- 5%) and reduced segmental amplitudes from 80 +/- 36 gray level intensity at baseline to 53 +/- 34 in segments developing mild to moderate hypokinesia, and from 93 +/- 36 to 35 +/- 28 gray level intensity in segments developing severe hypokinesia. Shifts in segmental phase angles correlated better with dynamic shifts in segmental fractional area shortening than did changes in wall motion score (r = -0.65 vs. r = 0.52, p < 0.001).

CONCLUSIONS

Echocardiographic Fourier phase imaging can be used to evaluate ischemia-related regional wall asynergy, displaying contraction sequence and magnitude in a simple, objective format.

Improved detection of abnormal left ventricular wall motion using tomographic radionuclide ventriculography compared with planar radionuclide and single plane contrast ventriculography

Tomographic radionuclide ventriculography is a technique which could have major advantages over conventional planar imaging, such as better assessment of ventricular wall motion abnormalities. This possibility was therefore investigated in 100 consecutive patients undergoing routine cardiac catheterization. Following angiography, planar blood pool images were conventionally acquired and tomographic imaging performed using the Aberdeen Section Scanner. All derived wall motion data were subsequently analysed in an objective and blinded manner. The mean age was 56 (range 33-71) and 79% were male. 67 patients had experienced prior myocardial infarction, 27 were categorized as having significant and six insignificant coronary artery disease. The detection rates for patients with prior myocardial infarction were 95% for angiography, 57% for planar imaging and 90% for tomography. Even taking patients with only prior anterior myocardial infarction, the detection rates were 94%, 63% and 91% respectively. For those residual patients with significant coronary artery disease, the rates were 7%, 0% and 59% respectively. Overall for the detection of patients with significant coronary artery disease, the sensitivity was 70%, 40% and 81% respectively. Patients with insignificant coronary artery disease did not demonstrate any abnormalities using any method. These results demonstrate that tomography and angiography have similar detection rates in the presence of significant coronary artery disease and both are superior to planar imaging.

The scintigraphic characteristics of ventricular pre-excitation through Mahaim fibers with the use of phase analysis

The phase image pattern of blood pool scintigrams was blindly assessed in 11 patients exhibiting conduction through Mahaim pathways, including 6 nodoventricular and 5 fasciculoventricular. These patterns were compared with the phase image findings in normal subjects, patients with left and right bundle branch block in the absence of pre-excitation and patients with pre-excitation through atrioventricular (AV) connections. In all patients with a Mahaim pathway, the site of earliest phase angle was septal or paraseptal. Phase progression was asymmetric and the pre-excited ventricle demonstrated the earliest mean ventricular phase angle in 10 of 11 patients. This pattern, and the associated ventricular phase difference, appeared to vary from that in normal subjects and in those with a septal AV connection, in whom phase progression is generally symmetric. Scintigraphic phase analysis provided localizing information and presented patterns consistent with Mahaim pathways. Although not able to differentiate among Mahaim pathway subtypes, these phase patterns differed from those in normal subjects, those with right and left lateral free wall pathways and most patients with a septal AV pathway. However, the phase pattern of patients with a Mahaim pathway may not differ from that of patients with a septal AV connection displaying an asymmetric pattern of phase progression, or those with left and right bundle branch block in the absence of pre-excitation. Objective, yet imperfect phase measurements supported these differences. Such image findings may complement the often complex electrophysiologic evaluation of patients presenting with pre-excitation.

Diagnosis of exercise-induced left bundle branch block at rest by scintigraphic phase analysis

Accurate diagnosis of diseases of the ventricular conducting system is essential for their appropriate therapy. Some conduction abnormalities, such as exercise-induced left bundle branch block (EX-LBBB), are not apparent on resting electrocardiograms. Phase analysis of rest and exercise radionuclide ventriculograms (RVG's) was used to compare four EX-LBBB patients with six normal controls. All patients had normal resting electrocardiograms, ejection fractions, and visually normal wall motion. First harmonic phase images were generated reflecting the timing of ventricular contraction. Dynamic phase displays were reviewed and graded in a blinded fashion by three independent experienced observers. Phase angle histograms of the right and left ventricle were determined for both resting and exercise images. The mean phase angle and standard deviation were also calculated for each ventricle. Visual grading of the resting phase images failed to show a significant difference between normal patients and patients with EX-LBBB. Quantitative analysis, however, revealed a significant difference in mean phase angle differences (LV-RV) in resting studies: 0.8 degrees (+/- 1.9 degrees SEM) in normals versus 9.3 degrees (+/- 2.3 degrees SEM) in EX-LBBB patients (P less than 0.03). Exercise accentuated the phase angle differences: 1.8 degrees in normals vs. 31.2 degrees in EX-LBBB patients (P less than 0.001). Quantitative phase analysis of resting RVG's permits the diagnosis of cardiac conduction disease that is not apparent on the resting EKG and may result in better monitoring and treatment.