Patterns of ventricular contraction in patients with conduction abnormality studied by radionuclide angiocardiography

Left ventricle and mitral valve reverse remodeling in response to cardiac resynchronization therapy in nonischemic cardiomyopathy

BACKGROUND

Cardiac resynchronization therapy (CRT) improves left heart geometry and function in nonischemic cardiomyopathy (NICMP). We aimed to detail the effects of CRT on left ventricular (LV) and mitral valve (MV) remodeling using 2-dimensional transthoracic echocardiography.

METHODS

Forty-five consecutive patients with NICMP who underwent CRT implantation between 2009 and 2012, and had pre-CRT and follow-up echocardiograms available, were included. Paired t test, linear and logistic regression, and Kaplan-Meier survival analyses were used for statistical assessment.

RESULTS

The mean age and QRS duration were 60 years and 157 ms, respectively, and 13 (28.9%) were female. At a mean follow-up of 3 years, there were 22 (48.9%) "CRT responders" (≥15% reduction in LV end-systolic volume index [LVESVi]). Significant improvements were observed in LV ejection fraction (26.3% vs 34.3%) and LVESVi (87.7 vs 71.1 mL/m² ), as well as mitral regurgitation vena contracta width, MV tenting height and area, and end-systolic interpapillary muscle distance. Five-year actuarial survival was 87.5%. Multivariate regression analyses revealed the pre-CRT LVESVi (β = 0.52), and MV coaptation length (β = -0.34) and septolateral annular diameter (β = 0.25) as good correlates of follow-up LVESVi. Variables associated with CRT response were pre-CRT MV coaptation length (OR 1.75, 95% CI 1.0-3.1) and posterior leaflet tethering angle (OR 1.07, 95% CI 1.0-1.14), irrespective of baseline QRS morphology and duration (all P < .05).

CONCLUSIONS

Cardiac resynchronization therapy improves LV and MV geometry and function in half of patients with NICMP, which is paralleled by decreased mitral regurgitation severity. The extent of pre-CRT LV remodeling and MV tethering are associated with CRT response.

Effect of Left Bundle Branch Block on Systolic and Diastolic Function of Left Ventricle in Heart Failure

This study was designed to examine the effect of left bundle branch block (LBBB) on systolic and diastolic function of the left ventricle (LV) in patients with heart failure and in normal subjects. Thirty-six patients with heart failure and LBBB (group I), 36 patients with heart failure with normal conduction (group II), and 41 subjects with isolated LBBB (group III) were compared. Coronary angiography was performed and LV end diastolic pressure was calculated. Echocardiography was performed on all patients. LV ejection fraction and mean rate of circum ferential shortening were calculated. The following Doppler parameters were evaluated: peak rapid filling velocity (E wave), peak atrial filling velocity (A wave), E- and A-wave integrals, E- wave acceleration time and deceleration time (EDT) and rates (EAR and EDR), the E/A ratio and its integral, and diastolic flow time (DT). The ejection time, isovolumetric relaxation time (IRT), and preejection period were measured using the aortic and mitral flow. LV end diastolic pressure was calculated as 28 ±4 mm Hg, 22 ±5 mm Hg, and 15 ±3 mm Hg in groups I, II, and III, respectively. Although the systolic function parameters in group III patients were different, the diastolic function parameters of group II were found to be quite similar to those of group III patients. Comparison of group I patients with group II patients showed that there was a similarity between LV systolic function parameters while the diastolic function parameters were different (E/A, p = 0.004; EAR, p<0.001; EDR, p<0.001; EDT, p<0.001; IRT, p = 0.024; DT, p=0.03). In conclusion, this study evaluating the effects of LBBB in normal subjects (isolated LBBB) and patients with heart failure showed that LBBB causes diastolic function impairment in normal subjects similar to those of patients with heart failure, and also increases impairment of diastolic function in patients with heart failure.

Cardiac resynchronization therapy: the issue of non-response

Cardiac resynchronization therapy reduces mortality and morbidity in heart failure patients with wide QRS and severe impairment of left ventricular systolic function, who are symptomatic despite optimal medical therapy. However, a high percentage of patients fail to show clinical or echocardiographic response to this treatment. Beyond current selection criteria, other elements, such as QRS duration and morphology, concomitant medical therapy, degree of right ventricle dysfunction, myocardial viability, presence of left ventricular dyssynchrony, and associated renal dysfunction, play a crucial role in modulating the response to cardiac resynchronization. Consequently, they should be part of the standard pre-implant evaluation, as they could be used to identify patients who are very unlikely to be responders.

EANM/ESC guidelines for radionuclide imaging of cardiac function

Radionuclide imaging of cardiac function represents a number of well-validated techniques for accurate determination of right (RV) and left ventricular (LV) ejection fraction (EF) and LV volumes. These first European guidelines give recommendations for how and when to use first-pass and equilibrium radionuclide ventriculography, gated myocardial perfusion scintigraphy, gated PET, and studies with non-imaging devices for the evaluation of cardiac function. The items covered are presented in 11 sections: clinical indications, radiopharmaceuticals and dosimetry, study acquisition, RV EF, LV EF, LV volumes, LV regional function, LV diastolic function, reports and image display and reference values from the literature of RVEF, LVEF and LV volumes. If specific recommendations given cannot be based on evidence from original, scientific studies, referral is given to "prevailing or general consensus". The guidelines are designed to assist in the practice of referral to, performance, interpretation and reporting of nuclear cardiology studies for the evaluation of cardiac performance.

Use of left ventricular pacing in heart failure: evaluation by gated blood pool imaging

BACKGROUND

Left ventricular (LV) pacing has been suggested to complement other forms of therapy in patients with heart failure.

METHODS AND RESULTS

We investigated 17 patients (15 men, 2 women, aged 68 +/- 6 years, 10 ischemic and 7 primary dilated cardiomyopathy) with heart failure (13 were in New York Heart Association class IV and 4 in class III). One month after LV pacer implantation, 12 patients reported clinical improvement (mean class 3.7 before pacing vs 2.6 with LV pacing; P = .001). We report the results of 3 equilibrium-gated blood pool studies performed in each patient, 1 before pacing and 2 after pacer implantation (1 with pacing on, and 1 after turning off the pacer). LV pacing did not modify LV ejection fraction. Phase analysis demonstrated a significant decrease of the interventricular phase shift (delta(pi)) with LV pacing (no pacing, delta(pi) = 8.99 degrees +/- 19.05 degrees; delta7n= -0.97 degrees +/- 27.85 degrees with LV pacing). Clinical improvement was observed in patients with an initial positive delta(pi) that decreased with pacing and/or an initial LV phase standard deviation >50 degrees that decreased with pacing.

CONCLUSION

LV pacing induces interventricular and intraventricular synchronization. A decrease of the interventricular phase shift seems to be the most important predictor of functional recovery for paced patients with heart failure.

Comparison between planar and tomographic radionuclide ventriculography for detecting inferior wall motion abnormalities

Gated planar radionuclide ventriculography is routinely used for the detection of regional wall motion abnormalities of the left ventricle. However, for inferior wall motion abnormalities, sensitivity is known to be low in the left anterior oblique 'best septal' projection, although improved if a left posterior oblique (LPO) view is also acquired. Gated tomography of the cardiac blood pool is now available. This study compared the sensitivity of planar 'best septal' projection, LPO and tomographic radionuclide ventriculography in the detection of inferior wall motion abnormalities. Thirty-two patients consisting of 18 with previous inferior myocardial infarction and 14 normal controls were studied. All patients underwent equilibrium planar 'best septal', planar LPO and then tomographic radionuclide ventriculography. Inferior wall motion abnormality was detected in 'best septal' in eight (44%) patients, LPO in 12 (67%) and tomography in 17 (94%) patients, respectively. Tomographic radionuclide ventriculography was best at detecting inferior wall motion abnormality while planar LPO projection is better than 'best septal' projection.

Does Fourier phase shift correlate with conduction delay in bundle branch block?

Fourier analysis of radionuclide ventriculography is adept at qualitatively demonstrating interventricular conduction delay in bundle branch block. In this study of eighteen patients, there is a considerable individual variation when the phase delay is expressed as an absolute conduction delay (milliseconds). Much of this variability persists after curve representation by the Fourier function has been optimized. It is suggested that this variability is due to differences in the shape of the right and left ventricular time-activity curves, reflecting differences in contraction and relaxation in the two ventricles. Such differences may be more pronounced in some subjects than others. These results suggest that absolute conduction delay cannot be reliably achieved by this method.

A study of ventricular contraction sequence in complete right bundle branch block by phase analysis

Twenty-four patients with complete right bundle branch block (CRBBB) combined with and without left axis deviation (LAD) on ECG, were compared with 17 normal subjects to evaluate the right ventricular contraction sequence and pattern in detail. Blood pool scintigrams were obtained in the left anterior oblique projection, and these images were analyzed by first component Fourier harmonics. In the normal subjects, the phase value distribution representing the pattern of ventricular contraction was almost homogeneous in both the right and left ventricles (RV & LV). In the CRBBB patients without LAD, the phase images showed apparent phase delay in the right ventricle. In the CRBBB patients with LAD, the phase images showed many different contraction patterns varying from normal to RV phase delay, owing to the effects of the hemi-block. Quantitative analysis of the absolute values, showed that the mean (RV-LV) value was 6.6 +/- 8.4 msec in the normal subjects. In the CRBBB patients without LAD, the duration of the QRS complex correlated with the mean (RV-LV) value, whereas no difference was observed between the duration of the QRS complex and the standard deviation of the right ventricle. Using phase analysis the degree of the RBBB can be determined from the phase images, and can be quantitatively analyzed as in electrical studies.

Relation between mean ventricular phases in chronic cor pulmonale measured by radionuclide ventriculography

ECG-gated equilibrium radionuclide ventriculography was performed in 17 patients with pulmonary heart disease (Cp) and in 11 healthy subjects (Nm). Fourier analysis was applied to the time activity curve in each pixel, and the phase and amplitude of the basic frequency were computed. From the pixel-by-pixel values, the mean phase of each ventricle was calculated. It was found that the difference between mean phase of right and left ventricle (psi(R-L)] was significantly greater in Cp (+13.8 degrees +/- 7.8 degrees) than in Nm (-0.3 degrees +/- 3.9 degrees). This difference was almost twice as great in Cp with RV failure (+15.9 degrees +/- 7.8 degrees) than in those without it (+8.8 degrees +/- 5.1 degrees). Abnormally increased psi(R-L) values were detected in about 70% of patients with Cp. Interventricular phase difference had a weak positive correlation with the amplitude of S wave in lead I of the ECG (r = 0.533). It is concluded that in most patients with Cp the phase of the RV contraction is delayed and that this delay may be connected with deterioration of RV performance.

Functional abnormalities in isolated left bundle branch block. The effect of interventricular asynchrony

Eighteen patients with isolated left bundle branch block (LBBB) were compared with 10 normal control subjects. Apexcardiograms, phonocardiograms, electrocardiograms, two-dimensional and dual M-mode echocardiograms, and radionuclide ventriculograms (RNV) were performed. There were no differences in the timing of right ventricular events between LBBB and normal subjects; however, striking delays in left ventricular systolic and diastolic events were apparent in the LBBB group. The delay was associated with shortening of left ventricular diastole and resultant increase in the ratio of right to left ventricular diastolic time in LBBB (1.2 +/- 0.08) compared with normal (1.0 +/- 0.06), p less than 0.0001. First heart sound (S1) amplitude, expressed as the ratio S1/S2, was decreased in LBBB compared with normal (0.67 +/- 0.2 compared with 1.34 +/- 0.25, p less than 0.01), in part due to wide separation of the valvular contributors to S1. The abnormal interventricular septal motion in LBBB corresponded to periods of asynchrony in contraction, ejection, end systole, and end diastole between right and left ventricles. Radionuclide ventriculograms revealed decreased regional ejection fraction of the septum in LBBB (40 +/- 16%) compared with 67 +/- 7% in normal subjects (p less than 0.001), while the apical and lateral regional ejection fractions were similar in the two groups. This loss of septal contribution resulted in a reduction in global ejection fraction in LBBB compared to normals (54 +/- 7% compared with 62 +/- 5%, p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effects of right atrial, right ventricular apex and atrioventricular sequential pacing on myocardial oxygen consumption and cardiac efficiency: a laboratory investigation

As the impact of cardiac pacing on myocardial energetics has not yet been established, this laboratory investigation was undertaken to evaluate the effects of right atrial (AP), right ventricular apex (VP) and atrioventricular sequential pacing (AVP) on cardiac energetics in a closed-chest model. Ninety-two pacing interventions were performed in ten anesthetized mongrel dogs with normal loading conditions and contractile states. The energetic effects of pacing were assessed in terms of myocardial oxygen consumption (MVO2), its hemodynamic determinants and cardiac efficiency. Efficiency was calculated as the ratio of O2-equivalent of external cardiac work to MVO2, using standard definitions. In the first series of experiments 36 intra-individual comparisons were made between AP and VP at identical rates (95-210 beats/min). In the second series AVP was compared to VP in 10 intra-individual comparisons at identical rates (109-190 beats/min). MVO2 was lower (p less than 0.001) during AP (8.30 +/- 2.14 ml O2/min.100 g) compared to VP (10.16 +/- 3.15 ml O2/min.100 g) at the same rate (158 +/- 32 beats/min). Efficiency (p less than 0.001) was considerably higher during AP (21.6 +/- 5.7%) compared to VP (12.8 +/- 5.9%). During AVP, MVO2 (10.85 +/- 1.76 ml O2/min.100 g) was not significantly different from VP (10.57 +/- 1.34 ml O2/min.100 g) at the same rate (146 +/- 25 beats/min). Hemodynamics were superior with AVP compared to VP. Efficiency was significantly higher (p less than 0.01) with sequential (15.4 +/- 3.9%) as compared to ventricular pacing (12.0 +/- 3.2%). In conclusion, this study indicated that VP exerts disadvantageous effects on MVO2 and cardiac efficiency. AP has beneficial effects on cardiac energetics because it improves the relationship between mechanical performance of the heart and its energy requirements. AVP results in a higher efficiency than VP due to superior hemodynamics, despite MVO2 levels comparable to those of VP. The mechanism of energy waste with right ventricular apex pacing is probably related to an asynchronous contraction in the ventricular myocardium due to a nonphysiological spread of excitation.

Quantitative radionuclide angiocardiography

Quantitation of cardiac pump function using radionuclide angiocardiography provides objective information for the management of patients with heart disease. Left and right ventricular ejection fraction, stroke volume ratio, ejection rate, diastolic function, ventricular volume, parametric imaging, amplitude and phase analysis, and shunt quantification can be measured from the radionuclide angiocardiogram at rest, during exercise, and during pharmacologic interventions. This review describes these methods and discusses their reliability and their role in the clinical assessment of patients with cardiac disease.

Detection of electrocardiographically imperceptible ventricular pre-excitation by phase imaging

The sequence of ventricular contraction was studied by radionuclide phase imaging in 25 patients with Wolff-Parkinson-White syndrome. The studies were performed when no signs of precontraction were present in the electrocardiogram; in these cases pre-excitation was either intermittent or suppressable by injection of ajmaline. In 11 of the 16 patients with free wall accessory pathways, precontraction could be detected in spite of electrocardiographically absent pre-excitation. Discrete precontraction was seen also in 2 of the 9 patients with paraseptal accessory pathways. We conclude that antegrade conduction through the accessory pathway does not need to be completely blocked if signs of pre-excitation are absent on the electrocardiogram, and that phase imaging is, at least in some patients (especially those with free wall accessory pathways), a more sensitive technique for detection of pre-excitation (precontraction) than the electrocardiogram.

Radionuclide measurement of right ventricular function in atrial septal defect, ventricular septal defect and complete transposition of the great arteries

Right ventricular (RV) function was assessed in 80 patients with congenital heart disease by first-pass and gated equilibrium radionuclide angiography. In 30 patients with a ventricular septal defect (VSD) the mean RV ejection fraction (+/- standard deviation) was 64 +/- 7%. In 30 patients with a secundum atrial septal defect it was 61 +/- 9% and in 20 patients with surgically corrected complete transposition of the great arteries it was 49 +/- 13%. These values are in close agreement with values established with cineangiography for similar groups of patients. The mean ejection fraction in the group with transposition of the great arteries was significantly less than in the group with VSD (p less than 0.001). Phase analysis of the equilibrium studies showed that there was delayed RV contraction in many patients in the absence of conduction abnormalities. This delay was significantly greater in patients with atrial septal defect than in those with VSD (p less than 0.05). There was a strong correlation between size of left-to-right shunt and phase delay in patients with VSD (r = -0.72). Thus, first-pass gated radionuclide angiography provides a valid measurement of RV ejection fraction, and delayed RV contraction on phase analysis may be a sensitive index of early RV dysfunction.