Prevalence and predictors of mechanical dyssynchrony as defined by phase analysis in patients with left ventricular dysfunction undergoing gated SPECT myocardial perfusion imaging.

BACKGROUND: A novel method to quantify dyssynchrony using phase analysis of single-photon emission computed tomography (SPECT) myocardial perfusion imaging has been developed. We sought to determine the prevalence of SPECT-derived mechanical dyssynchrony, and we report clinical variables which predict mechanical dyssynchrony in patients with left ventricular dysfunction. METHODS: We used a count-based Fourier analysis method to convert the regional myocardial counts from discrete frames per cardiac cycle into a continuous thickening function which allows resolution of the phase of the onset of myocardial contraction. The standard deviation of left ventricular phases (Phase SD) describes the regional phase dispersion as a measure of dyssynchrony. Significant dyssynchrony was defined as Phase SD ≥ 43°. 260 patients with left ventricular ejection fraction ≤ 35% were examined. RESULTS: The prevalence of mechanical dyssynchrony in the entire cohort of patients studied was 52%. Univariate predictors of Phase SD were age (P = .03), black race (P = .0005), QRS duration, EF, EDV, summed stress score (SSS), and summed rest score (SRS) (all P = <.0001). Black race, male gender, QRS EF, and SRS were independent predictors of SPECT-based mechanical dyssynchrony. CONCLUSIONS: Significant SPECT-based mechanical dyssynchrony is relatively common among patients with left ventricular dysfunction. In a population of patients with predominantly ischemic heart disease referred for SPECT, a reduced EF, increasing QRS duration, severity and extent of myocardial scar on SPECT imaging are independent predictors of mechanical dyssynchrony and may serve to identify patients for dyssynchrony screening.

Use of phase analysis of gated SPECT perfusion imaging to quantify dyssynchrony in patients with mild-to-moderate left ventricular dysfunction.

BACKGROUND: CRT has been shown to be beneficial in the majority of patients with NYHA class III-IV symptoms, prolonged QRS duration, and an EF < or =35%. The use of imaging modalities to quantify dyssynchrony may help identify patients who may benefit from CRT, but do not meet current selection criteria. We hypothesize that patients with mild-to-moderate LV dysfunction have significant degrees of mechanical dyssynchrony. METHODS: We compared phase analysis measures of mechanical dyssynchrony from gated SPECT imaging in patients with mild-to-moderate LV dysfunction (EF 35-50%, n = 93), with patients with severe LV dysfunction (EF < or = 35%, n = 167), and with normal controls (EF > or = 55%, n = 75). Furthermore, we evaluated the relationships between QRS duration and dyssynchrony and determined the prevalence of dyssynchrony in patients with mild-moderate LV dysfunction. RESULTS: Patients with mild-moderate LV dysfunction have more dyssynchrony than normal controls (phase SD 37.7 degrees vs 8.8 degrees , P < .001 and bandwidth 113.5 degrees vs 28.7 degrees , P < .001), but less dyssynchrony than patients with severe LV dysfunction (phase SD 37.7 degrees vs 52.0 degrees , P < .001 and bandwidth 113.5 degrees vs 158.2 degrees , P < .001). In the cohort of patients with LV EF 35-50%, there were only weak correlations between QRS duration and dyssynchrony (phase SD, r = 0.28 and bandwidth, r = 0.20). There were 73 patients with LVEF 35-50% and QRS duration <120 milliseconds of which 21 (28.8%) had mechanical dyssynchrony. Overall, 37% of patients with mild-to-moderate LV dysfunction had significant degrees of mechanical dyssynchrony. CONCLUSIONS: This is the largest reported study evaluating mechanical dyssynchrony in patients with mild-moderate LV dysfunction using phase analysis of gated SPECT imaging. In this study, approximately one-third of patients with mild-to-moderate LV dysfunction had significant LV mechanical dyssynchrony. With further study, phase analysis of gated SPECT imaging may help improve patient selection for CRT.

Left ventricular mechanical dyssynchrony as assessed by phase analysis of ECG-gated SPECT myocardial perfusion imaging.

Cardiac resynchronization therapy (CRT) has shown benefits in patients with severe heart failure. The traditional criteria to select patients for CRT (NYHA class III or IV, depressed left ventricular (LV) ejection fraction, and prolonged QRS duration) result in at least 30% of the selected patients with no response to CRT. Recent studies with tissue Doppler imaging (TDI) have shown that the presence of LV dyssynchrony is an important predictor for response to CRT. Phase analysis has been developed to assess LV dyssynchrony from electrocardiography-gated single photon emission computed tomography (GSPECT) myocardial perfusion imaging (MPI). This technique uses Fourier harmonic functions to approximate regional wall thickening over the cardiac cycle and to calculate phases of regional onset of mechanical contraction (OMC). These OMC phases are obtained three-dimensionally over the left ventricle to generate an OMC phase distribution. Quantitative indices are calculated from the phase distribution to assess degree of LV dyssynchrony. This technique has been compared to other methods of measuring LV dyssynchrony and shown promising results in clinical evaluations. In this review, the phase analysis methodology is described and its up-to-date validations are summarized.

Evaluation of mechanical dyssynchrony and myocardial perfusion using phase analysis of gated SPECT imaging in patients with left ventricular dysfunction.

BACKGROUND: Using phase analysis of gated single photon emission computed tomography (SPECT) imaging, we examined the relation between myocardial perfusion, degree of electrical dyssynchrony, and degree of SPECT-derived mechanical dyssynchrony in patients with left ventricular (LV) dysfunction. METHODS AND RESULTS: We retrospectively examined 125 patients with LV dysfunction and ejection fraction of 35% or lower. Fourier analysis converts regional myocardial counts into a continuous thickening function, allowing resolution of phase of onset of myocardial thickening. The SD of LV phase distribution (phase SD) and histogram bandwidth describe LV phase dispersion as a measure of dyssynchrony. Heart failure (HF) patients with perfusion abnormalities have higher degrees of dyssynchrony measured by median phase SD (45.5 degrees vs 27.7 degrees, P < .0001) and bandwidth (117.0 degrees vs 73.0 degrees, P = .0006). HF patients with prolonged QRS durations have higher degrees of dyssynchrony measured by median phase SD (54.1 degrees vs 34.7 degrees, P < .0001) and bandwidth (136.5 degrees vs 99.0 degrees, P = .0005). Mild to moderate correlations exist between QRS duration and phase analysis indices of phase SD (r = 0.50) and bandwidth (r = 0.40). Mechanical dyssynchrony (phase SD >43 degrees) was 43.2%. CONCLUSIONS: HF patients with perfusion abnormalities or prolonged QRS durations have higher degrees of mechanical dyssynchrony. Gated SPECT myocardial perfusion imaging can quantify myocardial function, perfusion, and dyssynchrony and may help in evaluating patients for cardiac resynchronization therapy.

Emerging role of myocardial perfusion imaging to evaluate patients for cardiac resynchronization therapy.

Left ventricular (LV) dyssynchrony is an increasingly important consideration in the evaluation and management of patients with LV systolic dysfunction. Improvements in clinical status, LV remodeling, and survival have been demonstrated with the use of cardiac resynchronization therapy (CRT). The current selection criteria for patients who undergo CRT include the presence of severe LV dysfunction, significant heart failure symptoms, and electrical dyssynchrony on surface electrocardiography (wide QRS interval). However, up to 40% of patients who undergo CRT do not experience reductions in symptoms or LV functional improvement. Because electrical dyssynchrony is not synonymous with contractile or mechanical dyssynchrony, efforts have been made to more accurately quantify mechanical dyssynchrony in the hope of improving the selection of patients for CRT. These efforts have focused largely on echocardiographic measures of mechanical dyssynchrony. A novel method to quantify LV mechanical dyssynchrony has been developed using phase analysis of gated single photon-emission computed tomographic myocardial perfusion imaging. In conclusion, this report describes potential advantages, compared with other methods, of using myocardial perfusion imaging to evaluate patients for CRT; reviews the method of the phase analysis technique to quantify dyssynchrony; reviews the available evidence of its utility; and describes future directions in research.

Evaluation of combined cardiac positron emission tomography and coronary computed tomography angiography for the detection of coronary artery disease.

BACKGROUND: Coronary artery disease is a leading cause of morbidity and mortality. Multiple imaging modalities are used to screen for significant coronary artery disease. We report the concordance between coronary computed tomography angiography (CTA) and stress cardiac positron emission tomography (CPET) to detect significant coronary artery disease, the feasibility of combining CTA and CPET in one diagnostic test, and the ability of CTA and CPET to detect significant coronary artery disease by comparison with cardiac catheterization. METHODS: Forty patients were prospectively enrolled and imaged with a hybrid PET/CT scanner. Eighteen patients had cardiac catheterization data for comparison. Concordance of findings between diagnostic tests was assessed by examining overall percentage in agreement, area under the receiver operating characteristic curve, sensitivity, specificity, and positive and negative predictive values. RESULTS: The overall agreement between CTA and CPET for detecting significant coronary artery disease was 76.3% with a sensitivity and specificity of 91.7 and 69.2%, respectively. The overall agreement between CTA and cardiac catheterization for detecting significant coronary artery disease was 81.3% with a sensitivity and specificity of 81.8 and 80.0%, respectively. The overall agreement between CPET and cardiac catheterization for detecting significant coronary artery disease was 77.8% with a sensitivity and specificity of 76.9 and 80.0%, respectively. CONCLUSION: CTA and CPET can be performed in a single diagnostic test interval to simultaneously assess the extent of coronary artery disease and its hemodynamic significance. The sensitivity and specificity of CTA and CPET are similar to existing noninvasive screening tests.

Repeatability and reproducibility of phase analysis of gated single-photon emission computed tomography myocardial perfusion imaging used to quantify cardiac dyssynchrony.

BACKGROUND: A novel method to quantify dyssynchrony has been developed using phase analysis of gated single-photon emission computed tomography perfusion imaging. We report on the effect of variability in image reconstruction on the phase analysis results (repeatability) and on the interobserver and intraobserver reproducibility of the technique. METHODS: Phase standard deviation (SD) and bandwidth are phase indices that quantify dyssynchrony. To evaluate repeatability, raw data sets were processed twice in 50 patients with left ventricular dysfunction and 50 normal controls. To determine the optimal processing method, two replicated phase analysis results were obtained using automated and manual base parameter placement. Reproducibility of the phase analysis was determined using the data from 20 patients. RESULTS: In normal controls, manual base parameter placement improves repeatability of the phase analysis as measured by the mean absolute difference between two reads for phase SD (12.0 degrees vs. 1.2 degrees , P<0.0001) and bandwidth (33.7 degrees vs. 3.6 degrees , P<0.0001). Repeatability is better for normal controls than for patients with left ventricular dysfunction for phase SD (1.2 degrees vs. 6.0 degrees , P<0.0001) and bandwidth (3.6 degrees vs. 26.5 degrees , P<0.0001). Reproducibility of the phase analysis is high as measured by the intraclass correlation coefficients for phase SD and bandwidth of 0.99 and 0.99 for the interobserver comparisons and 1.00 and 1.00 for the intraobserver comparisons. CONCLUSION: A novel method to quantify dyssynchrony has been developed using gated single-photon emission computed tomography perfusion imaging. Manual base parameter placement reduces the effect that variability in image reconstruction has on phase analysis. A high degree of reproducibility of phase analysis is observed.

Assessment of left ventricular mechanical dyssynchrony by phase analysis of ECG-gated SPECT myocardial perfusion imaging.

Cardiac resynchronization therapy (CRT) has shown benefits in patients with severe heart failure. However, at least 30% of patients selected for CRT by use of traditional criteria (New York Heart Association class III or IV, depressed left ventricular [LV] ejection fraction, and prolonged QRS duration) do not respond to CRT. Recent studies with tissue Doppler imaging have shown that the presence of LV dyssynchrony is an important predictor of response to CRT. Phase analysis has been developed to allow assessment of LV dyssynchrony by gated single photon emission computed tomography myocardial perfusion imaging. This technique uses Fourier harmonic functions to approximate regional wall thickness changes over the cardiac cycle and to calculate the regional onset-of-mechanical contraction phase. Once the onset-of-mechanical contraction phases are obtained 3-dimensionally over the left ventricle, a phase distribution map is formed that represents the degree of LV dyssynchrony. This technique has been compared with other methods of measuring LV dyssynchrony and shown promising results in clinical evaluations. In this review the phase analysis methodology is described, and its up-to-date validations are summarized.

Evaluation of left ventricular mechanical dyssynchrony as determined by phase analysis of ECG-gated SPECT myocardial perfusion imaging in patients with left ventricular dysfunction and conduction disturbances.

BACKGROUND: Cardiac resynchronization therapy (CRT) is approved for the treatment of patients with advanced systolic heart failure and evidence of dyssynchrony on electrocardiograms. However, a significant percentage of patients do not demonstrate improvement with CRT. Echocardiographic techniques have been used for more accurate determination of dyssynchrony. Single photon emission computed tomography (SPECT) myocardial perfusion imaging has not previously been used to evaluate cardiac dyssynchrony. The objective of this study is to evaluate mechanical dyssynchrony as described by phase analysis of gated SPECT images in patients with left ventricular dysfunction, conduction delays, and ventricular paced rhythms. METHODS AND RESULTS: A novel count-based method is used to extract regional systolic wall thickening amplitude and phase from gated SPECT images. Five indices describing the phase dispersion of the onset of mechanical contraction are determined: peak phase, phase SD, bandwidth, skewness, and kurtosis. These indices were determined in consecutive patients with left ventricular dysfunction (n = 120), left bundle branch block (n = 33), right bundle branch block (n = 19), and ventricular paced rhythms (n = 23) and were compared with normal control subjects (n = 157). Phase SD, bandwidth, skewness, and kurtosis were significantly different between patients with left ventricular dysfunction, left bundle branch block, right bundle branch block, and ventricular paced rhythms and normal control subjects (all P < .001) Peak phase was significantly different between patients with right ventricular paced rhythms and normal control subjects (P = .001). CONCLUSIONS: A novel SPECT technique for describing left ventricular mechanical dyssynchrony has been developed and may prove useful in the evaluation of patients for CRT.

Hemolytic anemia: a rare but potentially serious adverse effect of captopril.

Captopril was the first oral angiotensin-converting enzyme (ACE) inhibitor available and, as such, has been extensively studied and in clinical use for many years. Several studies have defined captopril's efficacy in the treatment of congestive heart failure (CHF) as well as determined its safety profile. The most common adverse hematologic reactions associated with captopril use include neutropenia and agranulocytosis. This paper describes an uncommon and a potentially serious hematologic side effect associated with captopril-hemolytic anemia.

The effect of foot placement on sit to stand in healthy young subjects and patients with hemiplegia.

OBJECTIVE: To determine the effect of altering the foot placement of the dominant limb in young healthy subjects and the uninvolved limb of subjects with hemiplegia on their ability to perform sit to stand (STS). DESIGN: Controlled biomechanical experiment. SETTING: Research laboratory of a university health science center. PARTICIPANTS: Nonrandom convenience sample of 10 healthy and 10 subjects with hemiplegia. Respective mean ages were 26 and 59 years. All patients with hemiplegia could ambulate and STS independently. The mean time since the stroke was 3.6 years. INTERVENTIONS: Subjects came from a sitting to a standing position under 3 different conditions: (1) normal condition, where both limbs were placed in 100 degrees of knee flexion; (2) limb extended condition, where the dominant or uninvolved limb was extended to 75 degrees of knee flexion; and (3) limb elevated condition, where the dominant or uninvolved limb was placed on a dense foam support equal to 25% of the subject's knee height. MAIN OUTCOME MEASURES: Vertical and anteroposterior ground reaction forces (GRFs) and bilateral tibialis anterior and quadriceps electromyogram (EMG) activity. RESULTS: In the young subjects, the normally placed nondominant limb compensated for the extended or elevated position of the dominant limb. Peak GRFs and EMG amplitudes were all significantly greater for the nondominant limb. In patients with hemiplegia, the EMG of the involved limb increased 39% in the limb-elevated and -extended conditions compared with the normal condition. Respective values for the uninvolved limb decreased. GRFs were significantly greater for the uninvolved limb except for the vertical force in the limb-extended position. CONCLUSIONS: Muscle activity and GRFs can be influenced by altering the initial foot placement of the dominant or uninvolved limb during STS. These initial data have positive implications for the rehabilitation of patients with hemiplegia who could be taught to overcome a reduced ability to use their impaired limb after stroke.