Semi-quantitative myocardial perfusion MRI in heart transplant recipients at rest: repeatability in healthy controls and assessment of cardiac allograft vasculopathy

BackgroundCardiac Allograft Vasculopathy (CAV) is a major cause of chronic cardiac allograft failure. Invasive coronary angiography (ICA) and intravascular ultrasound (IVUS) are the current diagnostic methods. Myocardial perfusion MRI has become a promising non-invasive method to evaluate myocardial ischemia, but has not been thoroughly validated in CAV. Our objective was to assess the repeatability of myocardial rest-perfusion MRI in healthy volunteers and its feasibility in detecting CAV in transplant patients (Tx).MethodsTwelve healthy volunteers and twenty transplant patients beyond the first year post- transplant underwent cardiac MRI at 1.5 T at rest including first-pass perfusion imaging in short axis (base, mid, apex) after injection of gadolinium. Volunteers underwent repeated cardiac MRI on different days (interval = 15.6 ± 2.4 days) to assess repeatability. Data analysis included semi-automatic contouring of endocardial and epicardial borders of the left ventricle (LV) and quantification of peak perfusion, time-to-peak (TTP) perfusion, and upslope of the perfusion curve.ResultsBetween scans and re-scans in healthy volunteers, peak signal intensity, slope, and TTP demonstrated moderate agreement (ICC = 0.53, 0.48, and 0.59, respectively; all, p < .001). Peak signal intensity, slope, and TTP were moderately variable with COV values of 23%, 42%, and 35%, respectively. Peak perfusion was significantly reduced in CAV positive (n = 9 Tx patients) compared to CAV negative (n = 11 Tx patients) groups (90.7 ± 27.0 vs 139.5 ± 30.2, p < .001).ConclusionCardiac MRI is a moderately repeatable method for the semi-quantitative assessment of first-pass myocardial perfusion at rest. Semi-quantitative surrogate markers of LV perfusion could play a role in CAV detection.     

Insulin resistance is a major determinant of myocardial blood flow impairment in anginal patients

Purpose

In patients with chest pain, stress-induced myocardial perfusion abnormalities are often the result of depressed myocardial blood flow (MBF) reserve. We investigated the relative contribution of cardiovascular risk factors and coronary atherosclerosis to MBF abnormalities in anginal patients.

Methods

We studied 167 patients with typical (n?=?100) or atypical (n?=?67) chest pain who underwent quantitative evaluation of MBF by PET at rest and after dipyridamole infusion, and quantitative coronary angiography (invasive or by 64-slice CT). Patients with left ventricular (LV) dysfunction (ejection fraction <45 %) were excluded. Coronary atherosclerosis of ≥50 % was defined as obstructive.

Results

At rest median MBF was 0.60 ml min^?1 g^?1, and after dipyridamole infusion median MBF was 1.22 ml min^?1 g^?1. MBF reserve was <2 in 77 of 167 patients (46 %). Coronary atherosclerosis was present in 67 patients (40 %), 26 with obstructive disease. In a univariate analysis several variables were associated with reduced MBF at rest, including male gender, coronary atherosclerosis and elevated LV end-diastolic diameter, and during hyperaemia, including male gender, insulin resistance (IR), smoking habit, LV ejection fraction and end-diastolic diameter. In a multivariate analysis, after adjustment for LV function and for pharmacological treatments, male gender was the only independent predictor of reduced MBF at rest (P?<?0.001), while male gender (P?=?0.003), IR (P?=?0.033) and coronary atherosclerosis (P?<?0.001) remained the only independent predictors of reduced hyperaemic MBF. IR (P?=?0.043) and coronary atherosclerosis (P?=?0.005) were the only predictors of depressed MBF reserve. Coronary atherosclerosis, male gender and IR showed additive effects on hyperaemic MBF.

Conclusion

In patients with chest pain and normal LV systolic function, IR, male gender and coronary atherosclerosis are independent and additive determinants of impaired hyperaemic MBF.     

Myocardial ischemia in the absence of obstructive coronary lesion: The role of post-stress diastolic dysfunction in detecting early coronary atherosclerosis

Background

The interactions between non-obstructive coronary atherosclerosis (<50% stenosis) and myocardial perfusion and functional parameters on myocardial perfusion imaging (MPI) have never been evaluated.

Methods and Results

One-hundred and ninety-five patients were submitted to stress-rest MPI and invasive coronary angiography. The presence of obstructive coronary lesions (>50% stenosis) was excluded. The summed stress score (SSS) was calculated in every patient. Moreover, the left ventricular (LV) ejection fraction (EF) and peak filling rate (PFR) were computed from gated MPI images as measures of systolic and diastolic functions. Sixty/195 patients (31%) showed the presence of non-obstructive atherosclerosis (>20% and <50% diameter reduction). Interestingly, they presented a higher SSS than those with normal coronary arteries (P < 0.001) despite a similar myocardial scar burden. If compared to patients with normal coronary arteries, those with non-obstructive atherosclerosis showed more abnormal post-stress PFR values (2.5 ± 0.9 vs 2.9 ± 0.8, P = 0.004), despite a similar EF. On multivariate analysis, the presence non-obstructive atherosclerosis was the only significant predictor (P = 0.026) of post-stress LV diastolic impairment, independently from perfusion parameters.

Conclusions

In patients without anatomically significant coronary lesions, the development of post-stress LV diastolic dysfunction on MPI associates with the presence of non-obstructive atherosclerosis on coronary angiography.

     

Sex-Related Differences in the Long-Term Outcomes of Patients with Femoropopliteal Arterial Disease Treated with the IN.PACT Drug-Coated Balloon in the IN.PACT SFA Randomized Controlled Trial: A Post Hoc Analysis

PurposeTo evaluate sex-related disparities in long-term outcomes of patients with peripheral artery disease (PAD) treated with IN.PACT drug-coated balloon (DCB) or percutaneous transluminal angioplasty (PTA).Materials and MethodsA post hoc analysis of the IN.PACT SFA trial was performed. Participants with Rutherford Clinical Classification 2–4 PAD and femoropopliteal artery lesions up to 18 cm long were randomly assigned to treatment with DCB (n = 220) or PTA (n = 111). Effectiveness outcomes were evaluated, including 36-month primary patency (freedom from binary restenosis and freedom from clinically driven [CD] target lesion revascularization [TLR]).ResultsIn the DCB group, women were significantly older (69.4 y ± 9.9) than men (66.4 y ± 9.1; P = .025). Mean reference vessel diameter (RVD) was significantly smaller in women (4.4 mm ± 0.68) compared with men (4.8 mm ± 0.89, P < .001). Primary patency was 65.4% in women and 71.8% in men (P = .302). Freedom from CD-TLR was 81.1% in women and 86.4% in men (P = .285). Women treated with PTA were older (70.4 y ± 8.3) than men (66.9 y ± 9.5; P = .063). Mean RVD was significantly smaller in women (4.2 mm ± 0.77) compared with men (4.9 mm ± 0.77, P < .001). Primary patency was 42.3% in women and 46.7% in men (P = .551). Freedom from CD-TLR was 59.4% in women and 75.5% in men (P = .109). No significant differences were noted in safety and mortality outcomes.ConclusionsIn both groups, women were older and had smaller vessels. Particularly in the PTA group, women had worse clinical outcomes, though not reaching statistical significance. Further evaluation is necessary to understand the disparate nature of disease progression and outcomes following endovascular treatment in women compared with men.     

Extent and severity of coronary artery disease by coronary CT angiography is associated with elevated left ventricular diastolic pressures and worsening diastolic function

BackgroundPatients with flow-limiting coronary stenoses exhibit elevated left ventricular end-diastolic pressure (LVEDP) and abnormal left ventricular (LV) relaxation.ObjectiveWe investigated the relationship of extent and severity of coronary artery disease (CAD) by coronary CT angiography (CTA) to LVEDP and measures of LV diastolic dysfunction.MethodsWe identified consecutive patients undergoing coronary CTA and transthoracic echocardiography who were assessed for diastolic function. CAD was evaluated on a per-patient, per-vessel, and per-segment basis for intraluminal diameter stenosis by using an 18-segment model (0 = none, 1 = 1%–49%, 2 = 50%–69%, and 3 = 70%–100%) and summed over segments to obtain overall coronary plaque burden (segment stenosis score [SSS]; maximum = 54). Transthoracic echocardiography evaluated mitral inflow E wave-to-A wave ratio, tissue Doppler early mitral annual tissue velocity axial excursion, stage of diastolic dysfunction, and LV dimensions and estimated LVEDP from the ratio of mitral inflow velocity to early mitral annular (medial) tissue velocity.ResultsFour hundred seventy-eight patients (57% women; mean age, 57.9 ± 14.6 years; 24.9% prior CAD) comprised the study population. Increasing per-patient maximal coronary stenosis, number of vessels with obstructive stenosis, and SSS were associated with increased LVEDP. The prevalence of advanced diastolic dysfunction increased with greater number of obstructive vessels. In multivariable analyses, SSS was associated with increased LVEDP (0.8 mm Hg per tertile increase in SSS, 0.5–1.1; P < .001); reduced E′ axial excursion (?0.3; 95% confidence interval [CI], ?0.5 to ?0.1; P = .001), increased LV mass index (1.6 g/m² per tertile increase in SSS; P = .04), and increased relative wall thickness (0.005; 95% CI, 0.004–0.009; P = .03), with consistent relationships persisting even among persons with per-patient maximal stenosis <50% and LV ejection fraction ≥55%.ConclusionsExtent and severity of obstructive as well as nonobstructive CAD by coronary CTA are associated with increased LVEDP and measures of diastolic dysfunction.     

A pilot study of 13N-ammonia cardiac PET imaging to assess subacute cardiotoxicity following adjuvant intensity-modulated radiotherapy for locally advanced breast cancer

Objective(1) Assess the feasibility of 13 N-ammonia cardiac PET (13 N-ammonia-PET) imaging in radiotherapy (RT) treatment position in locally-advanced breast cancer (LABC) patients. (2) Correlate pre−/post-RT changes in myocardial flow reserve (MFR) with the corresponding radiation heart dose.MethodsTen left-sided LABC patients undergoing Volumetric Modulated-Arc-Therapy (VMAT) to chest wall and regional lymph nodes underwent a rest/stress 13 N-ammonia-PET at baseline and (median) 13 months post-RT. Changes in cardiac functions and coronary artery Ca2+ scoring between baseline and follow-up were correlated with average RT dose to the myocardium,3 coronary territories, and 17 myocardial segments.ResultsEight (of 10) patients successfully completed the study. The average rest (stress) global MBF (ml.g-1.min-1) for baseline (follow-up) were 0.83 ± 0.25 (2.4 ± 0.79) and 0.92 ± 0.30 (2.76 ± 0.71), respectively. Differences in MBF, heart rate, blood pressure, and rate-pressure product (RPP) between baseline and follow-up were insignificant (P > 0.1).Strong (R = 0.79; P < 0.01) and moderate (R = 0.53; P = 0.37) correlation existed between MBF _Rest and MBF _Stress, and RPP respectively. Four patients showed a reduction in MFR of up to ~41% in follow-up studies, increasing to ~52% in myocardial segments close to high-radiation isodose lines in 5/8 patients. Agatston Ca + 2 scoring were zero in both baseline and follow-up in six patients; two patients exhibited mild increase in Ca + 2 on follow-ups (range:10–20).Rest and stress LVEF's were normal (>50) for all patients in both studies.ConclusionThe feasibility of 13 N-ammonia-PET imaging in treatment position of LABC patients was demonstrated. MFR at 1-year post-irradiation of the heart decreased in 50% of the patients. MFR may be a potential index for early detection of cardiotoxicity in BC patients receiving RT to the chest wall.     

Gated myocardial perfusion SPECT for preoperative risk stratification in patients with noncardiac vascular disease

Objective  Myocardial perfusion single photon emission computed tomography (SPECT) is useful for preoperative cardiac risk stratification. We investigated the value of preoperative pharmacologic stress electrocardiographic (ECG)-gated myocardial perfusion SPECT for noncardiac vascular surgery. Methods  To assess the perioperative cardiac risk for noncardiac vascular surgery, preoperative pharmacologic stress ECG-gated myocardial perfusion SPECT was performed in 211 consecutive patients who underwent noncardiac aortic surgery. We examined myocardial perfusion and left ventricular function by the quantitative gated SPECT (QGS), and the correlation with perioperative cardiac events was investigated. Results  Perioperative cardiac events occurred in 9 of 211 patients (4.3%). On the basis of univariate analysis, significant predictors for preoperative cardiac risk stratification included history of heart failure (P < 0.05), history of coronary artery revascularization (P < 0.05), summed stress score (SSS) (P < 0.0001), summed rest score (SRS) (P < 0.005), SSS ≥ 7 (P < 0.005), end-diastolic volume (EDV) ≥ mean + 2 standard deviation (SD) (134 ml for men and 93 ml for women) (P < 0.005), end-systolic volume (ESV) ≥ mean + 2 SD (60 ml for men and 37 ml for women) (p < 0.0001), left ventricular ejection fraction (EF) ≤ mean − 2 SD (48% for men and 55% for women) (P < 0.005) and wall motion abnormality (P < 0.05). On the basis of multivariate analysis, ESV ≥ mean + 2 SD was the only independent predictor for perioperative cardiac events (P < 0.005). Conclusions  Pharmacologic stress ECG-gated myocardial perfusion SPECT, which permits assessment of both myocardial perfusion and cardiac function, is useful for preoperative risk stratification of noncardiac vascular surgery.     

Positron emission tomography in the assessment of left ventricular function in healthy rats: A comparison of four imaging methods

Objective

To measure left ventricular (LV) function parameters in heart of healthy rats by three different positron emission tomography (PET) imaging techniques and by magnetic resonance imaging (MRI).

Methods

ECG-gated microPET examinations were obtained in seven healthy rats with 2-deoxy-2-[¹⁸F]fluoro-d-glucose (FDG) for calculation of LV-function from the blood-pool phase of the dynamic recording (FDG_BP), and also from the later myocardial uptake (FDG_Myo). On subsequent days, we re-measured LV-function using the novel blood-pool tracer ⁶⁸Ga-albumin (Alb_BP) and again by FDG (FDG_Myo2) in one setting. Cine-MRI examination provided the reference standard measurement.

Results

The mean LV ejection fractions (LVEF) were 56 ± 3 (FDG_BP), 55 ± 3 (FDG_Myo), 56 ± 3 (FDG_Myo2), 57 ± 3 (Alb_BP), and 57 ± 2 (MRI). There were good to excellent correlations found between the LVEF-values as compared to MRI reference standard for FDG_BP (r = 0.71), FDG_Myo (r = 0.86) and Alb_BP (r = 0.88). Both of the blood-pool methods significantly overestimated the magnitudes of end-diastolic-volume and end-systolic-volume, whereas FDG_Myo matched closely to the MRI reference standard. There was no significant bias for both blood-pool methods and a minor negative bias for FDG_Myo regarding the LV ejection fraction (LVEF) when compared to cine-MRI results. There was no significant difference between the means of FDG_Myo and FDG_Myo2 (P = .50).

Conclusions

Relative to reference standard MRI measurements of LVEF, there was excellent agreement between PET-based measurements, notably for the novel blood-pool tracer ⁶⁸Ga-albumin.     

Reference parameters for left ventricular wall thickness,thickening, and motion in stress myocardial perfusion CT: Global and regional assessment

PurposeTo use adenosine-induced stress CT myocardial perfusion imaging (CT-MPI) to determine normal reference values for left ventricle (LV) wall thickness (WT) and motion parameters.MethodsThis study included 106 Korean subjects (52 men and 54 women) who underwent CT-MPI due to chest pain, but were not found to have any detectable mild or severe coronary artery disease or myocardial perfusion defect. The following quantitative parameters were assessed on the CT-MPI according to a 17-segment model: LV myocardial thickness at end-systolic (WT_ES) and end-diastolic (WT_ED) phases, systolic wall thickening (SWT), and wall motion (WM). The associations of the measured parameters with the subjects' demographic characteristics and comorbidities were also analyzed.ResultsSeptal wall (7.2 mm) and basal-level (7.7 mm) LV myocardium demonstrated significantly higher WT (p < 0.001). SWT was highest in lateral (77.8%, p < 0.014) and apical (78.9%, p = 0.009) myocardium, while lateral (7.7 mm) and basal (6.7 mm) myocardium exhibited the greatest WM (p < 0.001). WT was significantly higher in men and younger (<60 years) subjects (all, p < 0.001). Hypertensive individuals presented with significantly higher SWT (79.9%, p = 0.024). LV WT exhibited statistically significant correlations (all positive, except for age) with age, height, weight, body surface area, body mass index, and systolic blood pressure (all, p < 0.010).ConclusionsThe present study provides CT-MPI reference values for LV myocardial WT, SWT, and WM measured on an adult Korean population. Knowledge of such normal reference measurements would be beneficial for the efficient interpretation of CT-MPI examinations in populations of Asian ethnicity.     

Sex- and age-specific differences in the long-term prognostic value of morphological plaque features detected by coronary computed tomography angiography

BackgroundAlthough sex- and age-specific differences in coronary plaque features detected by coronary computed tomography angiography (CCTA) are known, insufficient information regarding the long-term prognostic value of these findings exists.MethodsA total of 1615 patients with suspected but not previously diagnosed coronary artery disease (CAD) were examined by CCTA and coronary plaque features were assessed. The median follow-up period was 10.5 (IQR 9.2–11.4) years. Cox proportional-hazards analysis was used for the combined endpoint of cardiac death or nonfatal myocardial infarction.ResultsThe endpoint occurred more often in patients older than 65 years (5.66% vs. 2.05%; p = 0.00029) but similarly between female (3.34%) and male (3.07%) patients (p = 0.76). Both sexes displayed a similar prevalence for noncalcified (female vs. male: 0.77 ± 1.38 vs. 0.89 ± 1.41; p = 0.098) and low-attenuation (female vs. male: 2.6% vs. 4.37%; p = 0.096) plaques. As assessed by p for interaction CADRADS (p for interaction = 0.013), noncalcified plaques (p for interaction = 0.022) and low-attenuation plaques (p for interaction = 0.045) had a better primary endpoint association in women than in men. Concerning age, no difference in outcome association was apparent as evaluated by p for interaction.ConclusionCCTA demonstrates excellent long-term prognostic value irrespective of sex and age and independent from the higher prevalence of atherosclerotic plaques in men and patients older than 65 years. Although similarly prevalent in both sexes, noncalcified and low-attenuation plaques exhibit a better prognostic value in women.     

Quantitative thallium-201 and technetium 99m sestamibi tomography at rest in detection of myocardial viability in patients with chronic ischemic left ventricular dysfunction

Background  This study was designed to determine the most effective quantitative threshold for thallium-201 and technetium 99m sestamibi uptake on tomographic imaging after rest injection for the detection of myocardial viability in patients with chronic myocardial infarction. Methods and Results  Thallium and sestamibi cardiac tomography at rest was performed in 43 patients with chronic myocardial infarction and impaired left ventricular (LV) function undergoing coronary revascularization. In all patients, echocardiography and radionuclide angiography were performed at baseline and repeated 12 months later to evaluate recovery of regional LV function and LV ejection fraction, respectively. Optimal threshold cutoff points to separate reversible from irreversible dysfunction were determined by receiver operating characteristic analysis. When all dysfunctional segments were considered, the best cutoff point in the identification of reversible LV dysfunction for both thallium and sestamibi activity was 67%. When only akinetic or dyskinetic segments were considered, the best cutoff point in the identification of reversible LV dysfunction was 58% for thallium and 55% for sestamibi. In these segments, the area under the receiving operating characteristic curves constructed for thallium and sestamibi activity were 0.74±0.05 and 0.75±0.04, respectively (P=not significant). LV ejection fraction was 33%±7% at baseline and increased to 37%±7% after revascularization (P<.0001). A significant relation between the number of akinetic or dyskinetic but viable myocardial segments and revascularization-induced changes in LV ejection fraction was observed for both thallium (r=0.60, P<.0001) and sestamibi (r=0.64, P<.0001) imaging. Conclusions  In patients with chronic myocardial infarction, quantitative analysis of thallium and sestamibi activity on tomographic imaging at rest predicts recovery of regional and global LV dysfunction after revascularization procedures. The most effective quantitative threshold for detecting reversible LV dysfunction is comparable for thallium and sestamibi tomographic imaging. However, the optimal cutoff point is different for both tracers when all dysfunctional segments are considered or when the analysis is focused only on segments with more severe functional impairment (ie, akinetic or dyskinetic segments).     

Functional imaging in the assessment of myocardial infarction: MR imaging vs. MDCT vs. SPECT

Purpose

To intraindividually compare magnetic resonance (MR) imaging, ECG-gated multi-detector spiral computed tomography (MDCT) and gated single photon emission computed tomography (SPECT) for the evaluation of global and regional myocardial function and the identification of myocardial perfusion abnormalities.

Materials and methods

Nine patients (8 men; 55.1 ± 8.9 years) with a history of myocardial infarction (MI) were included in this retrospective study. All patients had undergone segmented k-space steady state free precession MR imaging, ^99mTc-MIBI gated myocardial perfusion SPECT and contrast enhanced ECG-gated 16-MDCT. Ventricular volumes and ejection fraction (EF) were calculated. Left ventricular (LV) wall motion at rest was analyzed. For SPECT and arterial phase MDCT perfusion abnormalities were assessed. Data was compared with Lin's concordance-correlation coefficient (ρ_c), Bland-Altman plots and kappa statistics.

Results

For EF, there was an excellent concordance and correlation (ρ_c = 0.99) between SPECT (EF = 41.7 ± 10.4%), MDCT (EF = 42.2 ± 11.1%), and MR imaging (EF = 41.9 ± 11.4%). Considering MR imaging as standard of reference, MDCT (κ = 0.86) is superior to SPECT (κ = 0.51) for the assessment of the regional wall motion at rest. There was a good agreement between SPECT and MDCT regarding the detection of perfusion abnormalities (κ = 0.62).

Conclusion

MDCT, MR imaging, and SPECT allow for the reliable assessment of global and regional left ventricular function in patients with a history of MI. MDCT also allows to some extent for the detection of perfusion abnormalities. With its potential to assess both, the coronary arteries as well as the myocardium, MDCT a promising modality for the comprehensive diagnostic work-up in patients with suspected myocardial ischemia.     

Postoperative Functional Outcome After Off-Pump Versus On-Pump Coronary Artery Bypass Grafting Using Gated Myocardial SPECT: A Comparison by Propensity Score Analysis

Purpose

We evaluated the short-term and mid-term differences in perfusion and function after off-pump and on-pump coronary artery bypass grafting (CABG) using gated myocardial single photon emission computed tomography.

Materials and Methods

A total of 70 patients with coronary artery disease who underwent CABG were included based on the propensity score matching results from 165 patients. Thirty-five patients underwent off-pump and 35 patients on-pump CABG. Rest ²⁰¹Tl/dipyridamole stress ^99 mTc-methoxyisobutylisonitrile gated single photon emission computed tomographies were performed preoperatively and postoperatively at short-term (103 ± 23 days after surgery) and mid-term follow-up (502 ± 111 days after surgery). Changes in left ventricular ejection fraction, end systolic volume, stress and rest segmental perfusion, and segmental wall thickening were compared between the two groups. The segments with preoperative rest ²⁰¹Tl uptake under 60% of maximum uptake were included in the segmental analysis.

Results

Left ventricular ejection fraction (P = 0.001) and end systolic volume (P = 0.008) showed significant improvement in both groups. There were no significant short-term and mid-term differences between the two groups in terms of left ventricular ejection fraction (P = 0.309) and end systolic volume (P = 0.938). Likewise, segmental rest (P = 0.178) and stress perfusion (P = 0.071), and systolic wall thickening (P = 0.241) showed significant improvement in both groups with similar time courses.

Conclusion

Off-pump CABG resulted in significant improvements in left ventricular ejection fraction, end systolic volume, and regional myocardial perfusion and function that are comparable to on-pump CABG at short-term and mid-term. Gated myocardial SPECT successfully revealed that off-pump CABG is as good as on-pump CABG from the viewpoint of myocardial perfusion and function.     

Utility of coronary CT angiography in outpatients with hypertrophic cardiomyopathy presenting with angina symptoms

BackgroundAngina is a frequent symptom in patients with hypertrophic cardiomyopathy (HCM); however, it is often not because of significant epicardial coronary artery stenosis. Coronary CT angiography (CCTA) is an excellent modality to rule out significant coronary artery stenosis in the low- and intermediate-risk patients; however, its value in patients with HCM has not been explored. We sought to assess the utility of CCTA in the assessment of patients with HCM and stable anginal symptoms and compare the incidence of epicardial coronary artery stenosis to an age- and gender-matched control group.MethodsConsecutive outpatients with HCM referred for CCTA over a 3-year period because of stable anginal symptoms (chest pain or shortness of breath) were identified retrospectively. Age- and gender-matched patients without HCM referred for CCTA because of similar symptoms over a 6-month period were used as controls. All patients had CCTA using an Aquilion ONE 320 scanner. The coronary arteries were evaluated independently by 2 blinded observers, and any luminal narrowing was scored quantitatively as follows: >70% = severe; 50% to 70% = moderate; <50% = mild; and none. For the HCM group, results of cardiac single-photon emission CT (SPECT) or cardiac magnetic resonance perfusion studies as well as catheter angiograms were recorded where available.ResultsA total of 91 patients with HCM and 91 controls were included. No significant difference in cardiac risk factors was present between the 2 groups. The CCTA was of diagnostic quality in all patients. The median (interquartile range) calcium score was lower in patients with HCM (0 [0–50] vs 2 [0–189]) but did not reach statistical significance (P = .23). The incidence of moderate-to-severe coronary artery stenosis was significantly lower in patients with HCM than in controls (6.6% vs 33.0%; P < .001). The incidence of left anterior descending artery luminal narrowing overall was also significantly lower in the HCM patients (7.0% vs 20.9%; P = .002). There was a higher incidence of myocardial bridging in patients with HCM (40.7% vs 6.6%; P < .001), with longer and deeper bridged segments. Among a subgroup of HCM patients (n = 24) who had either stress perfusion CMR or cardiac single-photon emission CT studies performed, 15 of 24 had false-positive perfusion abnormalities without evidence of luminal obstruction on CCTA.ConclusionWe demonstrate the use of CCTA for the assessment of stable anginal symptoms in patients with HCM. The incidence of moderate-to-severe coronary artery stenosis was significantly lower in our HCM patients in comparison to our age-matched, gender-matched, and risk factor–matched control group. Given the high incidence of false-positive findings on perfusion stress studies, we propose that CCTA may be useful for appropriate triage to coronary angiography in the HCM patient with anginal symptoms.     

Noncalcified atherosclerotic lesions with vulnerable characteristics detected by coronary CT angiography and future coronary events

BackgroundThe ability of coronary CT angiography (CTA) findings such as plaque characteristics to predict future coronary events remains controversial.ObjectiveWe investigated whether noncalcified atherosclerotic lesions (NCALs) detected by coronary CTA were predictive of future coronary events.MethodsA total of 511 patients who underwent coronary CTA were followed for cardiovascular events over a period of 3.3 ± 1.2 years. The primary end point was defined as hard events, including cardiac death, nonfatal myocardial infarction, or unstable angina that required urgent hospitalization. Early elective coronary revascularizations (n = 58) were excluded. The relationship between features of NCALs and outcomes is described.ResultsA total of 15 hard events (2 cardiac deaths, 7 myocardial infarctions, 6 cases of unstable angina that required urgent hospitalization) were documented in the remaining 453 patients with modest risks during a follow-up period of 3.3 ± 1.2 years. For these hard events, a univariate Cox proportional hazard model showed that the hazard ratio for the presence of >50% stenosis was 7.27 (95% CI, 2.62–21.7; P = .0002). Although the presence of NCAL by itself was not statistically significant, NCALs with low attenuation and positive remodeling (low-attenuation plaque [LAP] and positive remodeling [PR]; plaque CT number ≤34 HU and remodeling index ≥1.20) showed an adjusted hazard ratio of 11.2 (95% CI, 3.71–36.7; P < .0001). With C-statistics analysis, when both LAP and PR and >50% stenosis were added, the C-statistic was significantly improved compared with the basal model adjusted for age, sex, and log₂ (Agatston score +1) (0.900 vs 0.704; P = .0018).ConclusionsIdentification of NCALs with LAP and PR characteristics by coronary CTA provides additional prognostic information to coronary stenosis for the prediction of future coronary events.     

Impact of ischemia on left ventricular dyssynchrony by phase analysis of gated single photon emission computed tomography myocardial perfusion imaging

Background

There is increasing awareness of the value of phase analysis of gated tomographic myocardial perfusion imaging in assessing left ventricular (LV) dyssynchrony. A concern repeatedly raised in many studies is whether reversible defects in the stress images “ischemia” could affect the phase-derived standard deviation and bandwidth, the two commonly used dyssynchrony indices. We hypothesized that the stress and rest images should provide comparable information because the images are acquired 1 hour after the tracer injection.

Methods and Results

We studied two groups of patients with normal LV ejection fraction and no fixed perfusion defects. In group-1 (N = 20), the patients had reversible perfusion defects involving > 10% of the LV myocardium and in group-2 (N = 20), the patients had normal images. All patients underwent stress/rest-gated single photon emission computed tomography sestamibi imaging (the stress study was acquired with the lower dose) between January and March 2010. Patients with left bundle branch block or ventricular pacing were excluded. The patients in group-1 had a mean age of 61 ± 9 years, 65% were men, 75% Caucasians, and 70% had known prior coronary artery disease. The size of the reversible perfusion defect was 20 ± 13% (range 11%-50%) of the LV myocardium. The rest and stress phase-derived standard deviation (16 ± 6° vs 18 ± 8° and 16 ± 7° vs. 19 ± 6°) and the rest and stress bandwidth (42 ± 14° vs 46 ± 16° and 45 ± 17° vs 52 ± 12°), respectively, (P = NS for all) were similar in the two groups. The change (stress–rest) in standard deviation and bandwidth in groups 1 and 2 were not statistically significant (0.2 ± 3.1° vs 1.4 ± 4.7°, and 2 ± 13° vs 5 ± 13°, respectively, P = NS). There was no significant change from rest to stress in the standard deviation and the bandwidth in group-1 (P = .8 and .4, respectively) and group-2 (P = .2 and .08, respectively). There was no correlation between the size of the reversible perfusion defect and the change in phase standard deviation or bandwidth (r = 0.07 and 0.12, respectively, P = NS).

Conclusions

The presence of even a large reversible perfusion defect does not alter the indices of mechanical dyssynchrony by phase analysis. Further, comparable information is obtained whether using a low dose or a high dose of the radiotracer.     

Determinants of left ventricular mechanical dyssynchrony in patients submitted to myocardial perfusion imaging: A cardiac CZT study

Background

An interaction between coronary anatomy, myocardial perfusion, and left ventricular (LV) functional parameters in the development of mechanical LV dyssynchrony (LVD) has been suggested. This study examined the correlates of LVD in a large sample size of patients with known or suspected coronary artery disease (CAD) using cadmium-zinc-telluride camera.

Methods

Six-hundred and fifty-seven consecutive patients who underwent myocardial perfusion imaging (MPI) and coronary angiography were included. Coronary stenosis >70% was considered significant. LV perfusion and functional parameters were computed from MPI images. The presence of significant LVD was evaluated by phase standard deviation and histogram bandwidth.

Results

415/657 (63%) patients had significant CAD. LVD was present in 247 (38%) patients and was associated with the presence of a higher CAD burden (P < .001), more impaired measures of LV perfusion (P < .001), contractile function (P < .001), and larger LV volumes (P < .001). By multivariate analysis, the LV end-systolic volume index (P < .001) and ischemic burden (P < .001) were the strongest predictors of LVD independent of CAD extent and LV systolic dysfunction.

Conclusions

LVD is frequent in patients undergoing MPI for suspected or known CAD. Its presence is independent of CAD burden and LV systolic dysfunction, but is dependent on the presence of myocardial perfusion abnormalities and LV end-systolic volume.

     

11C]Acetate rest-stress protocol to assess myocardial perfusion and oxygen consumption reserve in a model of congestive heart failure in rats

This study describes an [¹¹C]acetate rest–stress method to obtain an indirect estimate of myocardial blood flow (MBF) and myocardial oxygen consumption (MVO₂) in rats. Doxorubicin cardiotoxicity was used to test the usefulness of this approach for the assessment of congestive heart failure.Methods[¹¹C]Acetate rest–stress studies have been used in clinical research to assess the capacity of the coronary arteries to respond to stress. In this article, we used this approach to assess the cardiotoxicity of doxorubicin in a rat model. The method was first validated in a group of healthy rats and then used to follow the effect of doxorubicin chemotherapy on cardiac function. The effect of doxorubicin on myocardial perfusion and oxygen consumption reserve was measured at rest and under dobutamine stimulation.ResultsValidation of the protocol showed a good correlation between the MBF and MVO₂ (r²=.68). The doxorubicin-treated group showed a significant (P=.04) decrease in cardiovascular perfusion reserve at 1.3±0.2 compared with the control animals at 1.6±0.2. Similar results were obtained for the MVO₂ reserve (treated 1.8±0.4 vs. controls 2.3±0.3; P=.02).ConclusionsWe describe an [¹¹C]acetate PET rest–stress protocol for the assessment of congestive heart failure in rats and its application to the follow-up of cardiotoxicity under doxorubicin chemotherapy. This is a rapid and reliable approach to the measurement of cardiac perfusion and oxygen consumption reserve that could be applied to the development of new strategies to reduce the cardiotoxicity of anthracycline.     

Relationship between myocardial perfusion abnormalities and contractile impairment in anginal patients

Background

A relationship between left ventricular (LV) contractile impairment and myocardial perfusion abnormalities has been suggested.

Methods and Results

Three-hundred and thirty-seven patients underwent myocardial perfusion imaging at CZT and coronary angiography. On scintigraphic images, the summed difference score (SDS) and LV-ejection fraction (EF) were computed. Patients were categorized as follows: Group-1 (LV-EF < 40%; 71 patients), Group-2 (LV-EF ≥ 40% and < 55%; 77 patients), and Group-3 (LV-EF ≥ 55%; 189 patients). Significant coronary artery disease (CAD; ≥50% stenosis) was recognized in 159/337 (47%) patients. Interestingly, while in Group-3 subjects an inverse relationship between SDS values and post-stress LV-EF was evident (P < .001), Group-1 patients presented a significant association between an increased SDS and more elevated post-stress LV-EF values (P = .009). Similarly, despite in the overall population an increasing severity of CAD was associated with higher SDS values (P < .001), this relationship disappeared in Group-1 patients (P = .298). At multiple regression analysis, after correction for CAD, LV dysfunction was negatively associated with an elevated SDS (P = .018). Conversely in patients with normal LV function and no history of myocardial infarction, CAD extent, and functional measures of stress-induced myocardial ischemia were strictly correlated.

Conclusions

Independently from CAD, a significantly impaired LV function associates with a lower prevalence of reversible ischemia.     

Comparison between exercise and trans-oesophageal atrial pacing in patients with coronary artery disease: technetium-99m methoxy isobutyl isonitrile simultaneous evaluation of ventricular function and myocardial perfusion

In this study we compared the results of exercise and trans-oesophageal atrial pacing (TAP) technetium-99m methoxyisobutyl isonitrile (^99mTc-SESTAMIBI) cardiac imaging in the evaluation of left ventricular (LV) function and myocardial perfusion in patients with angiographically proven coronary artery disease. Ten patients (8 men and 2 women, mean age 59 ± 6 years) were submitted to 3 separate injections of ^99mTc-SESTAMIBI, one under control conditions, one after exercise and one after TAP. LV ejection fraction, as measured by electrocardiogram (ECG) gated first pass, decreased from 49 ± 5 % under control conditions to 42 ±6% during exercise (P < 0.05 versus control) and to 43 ±8 % during TAP (P<0.05 versus control and insignificant change versus exercise). Segmental myocardial perfusion analysis was performed on a total of 150 myocardial segments. On both exercise and TAP ^99mTc-SESTAMIBI studies, 103 segments (69% of the total) were normal, 32 (21 %) had reversible, and 15 (10%) irreversible, perfusion defects. Relative regional tracer uptake was not statistically different between exercise and TAP in normal regions (91.1 ± 9.1 % versus 90.7 ± 8.5 %, respectively), in regions with reversible (61.9±12% versus 62.4±10.4%, respectively) and irreversible perfusion defects (55.8 ± 7.8 % versus 58.8 ± 9.5 %, respectively). Our results demonstrated that ^99mTc-SESTAMIBI TAP cardiac imaging shows similar results to ^99mTc-SESTAMIBI exercise myocardial scintigraphy in the assessment of LV function and myocardial perfusion in patients with coronary artery disease.This work was partially supported by a grant from the Italian National Council of Research (CNR) (Special Project Immagini Biomediche in-Vivo)