Relationship of myocardial substrate characteristics as assessed by myocardial perfusion imaging and cardiac reverse remodeling levels after cardiac resynchronization therapy

Background

Cardiac resynchronization therapy (CRT) can provide cardiac reverse remodeling (RR), which may include mechanical reverse remodeling (MRR) and/or electrical reverse remodeling (ERR). However, uncoupling of MRR and ERR is not uncommon, and the underlying mechanisms are not clear. This study aimed to evaluate the relationship of myocardial substrate characteristics as assessed by myocardial perfusion imaging (MPI) and cardiac RR post-CRT.

Materials and methods

Forty-one patients (26 men, mean age 66 ± 10 years) with heart failure received CRT for at least 12 months were assigned to three groups according to their levels of RR: I, MRR + ERR (ESV reduced ≥15 % and intrinsic QRS duration reduced ≥10 ms); II, MRR only (ESV reduced ≥15 %); and III, non-responder (the others). All the patients also underwent MPI under transient CRT-off to evaluate the intrinsic myocardial substrates, including myocardial scar, LV volumes and function, systolic dyssynchrony, and activation sequences. In addition, ventricular tachycardia (VT) and ventricular fibrillation (VF) detected by the CRT devices during follow-up periods were also recorded.

Results

Quantitative analysis of MPI showed that there were significant differences for scar burden [15.9 ± 9.5, 26.8 ± 16.1, and 45.6 ± 15.1 % for group I (n = 15), II (n = 16), and III (n = 10), respectively, p < 0.001], EDV (136.6 ± 64.9, 221.6 ± 123.9, and 351.8 ± 216.3 ml, p = 0.002), ESV (82.6 ± 59.8, 172.3 ± 117.2, and 293.3 ± 209.6 ml, p = 0.001), LVEF (44.9 ± 15.0, 25.6 ± 10.9, and 21.5 ± 11.7 %, p < 0.001), systolic phase SD (23.4° ± 10.3°, 36.0° ± 16.2°, and 57.0° ± 22.2°, p < 0.001), and bandwidth (72.5° ± 31.1°, 113.4° ± 56.4°, and 199.1° ± 90.1°, p < 0.001). Myocardial scar interfered with the normal propagation of mechanical activation, resulting in heterogeneous activation sequences. Compared with group II (MRR only), group I (ERR + MRR) had significantly less initial activation segments (1.9 ± 1.0 vs. 2.6 ± 0.7, p < 0.05) and shorter maximal contraction delay (46.9° ± 12.9° vs. 58.8° ± 18.5°, p < 0.05). During the periods of follow-up, 21 patients developed VT/VF, including only 1 patient (1 VT) in group I (6.7 %), 8 patients (7 VT and 1 VF) in group II (50 %), and 9 patients (7 VT and 5 VF) in group III (90 %).

Conclusion

The characteristics of myocardial substrates as assessed by MPI differed significantly between different levels of cardiac RR post-CRT. Myocardial scar played an important role in the development of ERR. Different cardiac RR levels contributed to different incidences of ventricular arrhythmia, and the combination of ERR and MRR provided highest anti-arrhythmic effects.

     

门控心肌灌注显像时相分析在心脏再同步化治疗中的应用

门控心肌灌注显像(GMPI)的时相分析技术评价左室机械不同步性前景看好,该方法的优点在于自动控制处理、重复性良好,并能得到灌注和预后信息。该文综述时相分析技术及其GMPI在心脏再同步化治疗中的应用价值。     

The potential of multi-slice computed tomography based volumetry for demonstrating reverse remodeling induced by cardiac resynchronization therapy

BackgroundMulti-slice computed tomography (MSCT) was proved to provide precise cardiac volumetric assessment. Cardiac resynchronization therapy (CRT) is an effective treatment for selected patients with heart failure and reduced ejection fraction (HFREF). In HFREF patients we investigated the potential of MSCT based wall motion analysis in order to demonstrate CRT-induced reversed remodeling.MethodsBesides six patients with normal cardiac pump function serving as control group seven HFREF patients underwent contrast enhanced MSCT before and after CRT. Short cardiac axis views of the left ventricle (LV) in end-diastole (ED) and end-systole (ES) served for planimetry. Pre- and post-CRT MSCT based volumetry was compared with 2D echo. To demonstrate CRT-induced reverse remodeling, MSCT based multi-segment color-coded polar maps were introduced.ResultsWith regard to the HFREF patients pre-CRT MSCT based volumetry correlated with 2D echo data for LV-EDV (MSCT 278.3 ± 75.0 mL vs. echo 274.4 ± 85.6 mL) r = 0.380, p = 0.401, LV-ESV (MSCT 226.7 ± 75.4 mL vs. echo 220.1 ± 74.0 mL) r = 0.323, p = 0.479 and LV-EF (MSCT 20.2 ± 8.8% vs. echo 20.0 ± 11.9%) r = 0.617, p = 0.143. Post-CRT MSCT correlated well with 2D echo: LV-EDV (MSCT 218.9 ± 106.4 mL vs. echo 188.7 ± 93.1 mL) r = 0.87, p = 0.011, LV-ESV (MSCT 145 ± 71.5 mL vs. echo 125.6 ± 78 mL) r = 0.84, p = 0.018 and LV-EF (MSCT 29.6 ± 11.3 mL vs. echo 38.6 ± 14.6 mL) r = 0.89, p = 0.007. There was a significant increase of the mid-ventricular septum in terms of absolute LV wall thickening of the responders (pre 0.9 ± 2.1 mm vs. post 3.3 ± 2.2 mm; p < 0.0005).ConclusionMSCT based volumetry involving multi-segment color-coded polar maps offers wall motion analysis to demonstrate CRT-induced reverse remodeling which needs to be further validated.     

Impact of imaging protocol on left ventricular ejection fraction using gated-SPECT myocardial perfusion imaging

Journal of Nuclear Cardiology - There are limited data on the impact of the imaging protocol (single-day stress-rest, SD, vs. dual-day, DD) on the change in left ventricular (LV) ejection fraction...     

门控心肌灌注断层显像相位分析评价健康人左室心肌收缩同步性

目的 应用美国Cedars-Sinai定量门控心肌断层显像(QGS)软件的相位分析技术定量分析健康人左室心肌收缩同步性.方法 对74名健康人[男41名,女33名,平均年龄(60±13)岁]进行运动-静息99Tcm-MIBI G-MPI.应用QGS软件对重建后的静息图像进行自动分析,获得左室心肌收缩同步性参数:相位直方图带宽(BW)和相位标准差(SD),比较不同性别及年龄组(＜60岁组,36名;≥60岁组,38名)间左室心肌收缩同步性的差别.测量左室17个节段的起始相位角度,确定左室心肌最早收缩部位,简单随机抽样选择40名受检者评价QGS软件相位分析技术在同一操作者和不同操作者间的重复性.数据分析采用两样本t检验和直线相关分析.结果 74名受检者左室BW和SD值分别为(37.22±11.71)°和(11.84±5.39)°.男性和女性BW及SD值差异均无统计学意义[BW:(36.00±9.70)°和(38.73±13.84)°;SD:(11.88±5.56)°和(11.79±5.26)°;t=0.96和-0.07,均P＞0.05).年龄≥60岁组较年龄＜60岁组BW宽[(39.95±12.65)°和(34.33±10.00)°;t=-2.11,P＜0.05];但2年龄组间SD差异无统计学意义[(11.18±4.31)°和(12.54±6.33)°;t=1.08,P＞0.05].74名受检者中,54名(73％)左室心肌收缩从基底部向心尖部扩散,仅20名(27％)由心尖部向基底部扩散.同一操作者2次操作及2名操作者间相位分析结果均相关(r=0.867～0.906,均P＜0.001).结论 健康人左室心肌收缩同步性良好,不同性别间无明显差异,年龄＜60岁者心肌收缩同步性较≥60岁者更好.QGS心脏相位分析软件是可定量评价左室心肌收缩同步性的工具,且重复性好.     

Myocardial substrate after cardiac resynchronization therapy and the risk of ventricular arrhythmias

Journal of Nuclear Cardiology -     

Nuclear imaging in cardiac resynchronization therapy.

Recently, cardiac resynchronization therapy (CRT) has become implemented in the treatment of patients with severe heart failure. Although the improvement in systolic function after CRT implantation can be considerable, 20%-30% of patients do not respond to CRT. Evidence is accumulating that the presence of left ventricular (LV) dyssynchrony is mandatory for a response to CRT. Since the early 1980s attempts have been made to assess cardiac dyssynchrony with nuclear imaging, and it has been reported recently that information on LV dyssynchrony can be obtained from gated myocardial perfusion SPECT with phase analysis. Other studies with SPECT have shown that extensive scar tissue will limit the response to CRT; similarly, it has been demonstrated that viable tissue (assessed with SPECT) in the target zone for the LV pacing lead (usually the lateral wall) is needed for a response to CRT. Moreover, studies with PET have provided insight into the changes in myocardial perfusion, metabolism, and efficiency after CRT. In the current review, a comprehensive summary is provided on the potential role of nuclear imaging in the selection of heart failure patients for CRT. The value of other imaging techniques is also addressed.     

Effect of transmyocardial laser revascularization on myocardial perfusion and left ventricular remodeling after myocardial infarction in rats

PURPOSE: To monitor perfusion changes in remote myocardium caused by transmyocardial laser revascularization (TMLR) and to investigate the influence of TMLR on left ventricular morphology and function. MATERIALS AND METHODS: The coronary arteries were ligated in 32 Wistar rats. Eight weeks later, cine magnetic resonance (MR) imaging was performed in both the treatment (n = 12) and control group (n = 8). TMLR was then performed in the remote myocardium in the treated group. Twelve weeks after myocardial infarction, cine MR imaging, including dobutamine-induced (10 micro g per kilogram of body weight per minute via the tail vein) stress, was repeated and followed with hemodynamic measurements in both groups and with perfusion MR imaging (in-plane resolution, 140 x 140 micro m) of the isolated heart at rest and during nitroglycerin-induced stress in the TMLR group (n = 10). RESULTS: Left ventricular dilatation and hypertrophy were enhanced in the TMLR group (change in end-diastolic volume at 8-12 weeks: control group, 24.6 micro L +/- 16.7 and TMLR group, 81.7 micro L +/- 15.7; change in left ventricular mass: control group, 54.5 mg +/- 19.2 and TMLR group, 124.1 mg +/- 30.7; P <.03 for both). Ejection fractions at rest were approximately equal (control group, 40% +/- 2; TMLR group, 38% +/- 2; P value not significant), but during dobutamine-induced stress, the ejection fraction was higher in the TMLR group (54.4% +/- 4.9; control group, 47.4% +/- 4.8; P <.05). TMLR-treated areas were better perfused than was untreated myocardium (difference in perfusion: TMLR-treated vs control region, 3.89 mL/min/g +/- 0.83 at rest vs 2.29 mL/min/g +/- 1.06 during nitroglycerin-induced stress; P <.05 for both). Hemodynamic measurements revealed no differences between groups. CONCLUSION: High-spatial-resolution perfusion MR imaging depicted a significant perfusion improvement after TMLR. Post-myocardial infarction remodeling of the left ventricle was found to be enhanced.     

Myocardial perfusion imaging using gated SPECT in heart failure patients undergoing cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) by biventricular pacing is indicated in patients with severe heart failure and left bundle branch block who remain symptomatic despite optimal medical therapy. The relationship between baseline resting perfusion pattern and hemodynamic response to CRT has not been fully investigated. We tested the usefulness of perfusion gated SPECT for baseline evaluation and follow-up of these patients. METHODS: In 20 patients, we performed gated SPECT before CRT and at the 3-mo follow up. Left ventricular (LV) ejection fraction (EF), end-diastolic (ED) and end-systolic (ES) volume indexes (VI), and wall motion score index (WMSI) were measured and compared with clinical outcome. RESULTS: One patient died before follow-up. The 19 remaining patients were classified into 1 of 2 groups according to the presence (group A) or absence (group B) of a significant severe perfusion defect at baseline before CRT. At the 3-mo follow-up, 6 of 10 group A and 8 of 9 group B patients had an improvement in New York Heart Association class. In both groups, quality of life, 6-min walking distance, and WMSI significantly improved. In group A, no significant change was registered in LVEF, LVEDVI, or LVESVI. In group B, LVEF increased from 23.1% +/- 8% to 27.1% +/- 11% (P < 0.03) and LVEDVI and LVESVI decreased from 159 +/- 70 mL to 135 +/- 68 mL (P < 0.02) and from 127 +/- 67 mL to 104 +/- 65 mL (P < 0.01), respectively. CONCLUSION: Perfusion gated SPECT appears useful to characterize and follow up candidates for CRT. Despite clinical improvement, patients with severe resting perfusion defects do not show significant improvement in LVEF or reduction in LV volumes.     

Left ventricular thrombus formation after acute myocardial infarction as assessed by cardiovascular magnetic resonance imaging

Introduction

Left ventricular (LV) thrombus formation is a feared complication of myocardial infarction (MI). We assessed the prevalence of LV thrombus in ST-segment elevated MI patients treated with percutaneous coronary intervention (PCI) and compared the diagnostic accuracy of transthoracic echocardiography (TTE) to cardiovascular magnetic resonance imaging (CMR). Also, we evaluated the course of LV thrombi in the modern era of primary PCI.

Methods

200 patients with primary PCI underwent TTE and CMR, at baseline and at 4 months follow-up. Studies were analyzed by two blinded examiners. Patients were seen at 1, 4, 12, and 24 months for assessment of clinical status and adverse events.

Results

On CMR at baseline, a thrombus was found in 17 of 194 (8.8%) patients. LV thrombus resolution occurred in 15 patients. Two patients had persistence of LV thrombus on follow-up CMR. On CMR at four months, a thrombus was found in an additional 12 patients. In multivariate analysis, thrombus formation on baseline CMR was independently associated with, baseline infarct size (g) (B = 0.02, SE = 0.02, p < 0.001). Routine TTE had a sensitivity of 21–24% and a specificity of 95–98% compared to CMR for the detection of LV thrombi. Intra- and interobserver variation for detection of LV thrombus were lower for CMR (κ = 0.91 and κ = 0.96) compared to TTE (κ = 0.74 and κ = 0.53).

Conclusion

LV thrombus still occurs in a substantial amount of patients after PCI-treated MI, especially in larger infarct sizes. Routine TTE had a low sensitivity for the detection of LV thrombi and the interobserver variation of TTE was large.     

Novel algorithm for quantitative assessment of left ventricular dyssynchrony with ECG-gated myocardial perfusion SPECT: useful technique for management of cardiac resynchronization therapy

Objectives  

Cardiac resynchronization therapy (CRT) is the established treatment for patients with chronic and severe heart failure, and it has been reported that the presence of left ventricular (LV) dyssynchrony is one of the most important factors which predict positive response of this therapy. In the present study, we developed new software algorithm for quantitative assessment of LV dyssynchrony from ECG-gated myocardial perfusion SPECT (GMPS), and evaluated its utility for the management of CRT.     

Duration and type of therapy for diabetes: Impact on cardiac risk stratification with stress electrocardiographic-gated SPECT myocardial perfusion imaging

Background  

Stress electrocardiogram(ECG)-gated single photon emission computed tomography (SPECT) imaging is highly effective in risk stratification of diabetic patients for adverse cardiac events. While patients with diabetes are predisposed to a more aggressive progression of vascular disease, the impact of its duration and type of therapy on risk stratification are unknown.     

Q-wave regression after acute myocardial infarction assessed by Tl-201 myocardial perfusion SPECT

BACKGROUND: The actual relationship between the interval change of myocardial thallium 201 (Tl-201) radioactivity in the infarct area and the pattern of Q-wave regression is still unknown. This study was conducted to evaluate their relationship after acute myocardial infarction (AMI). METHODS AND RESULTS: A total of 30 patients who had a first Q-wave AMI (11 without Q-wave regression and 19 with Q-wave regression) were retrospectively included. Two sets of 12-lead surface electrocardiograms and Tl-201 myocardial perfusion images were obtained 0 to 2 months and 14 to 84 months after the AMI event, respectively. The acute/subacute redistribution Tl-201 radioactivity was similar between the patients with and those without Q-wave regression. However, the patients with Q-wave regression had higher chronic redistribution Tl-201 radioactivity than those without Q-wave regression. Moreover, the patients with Q-wave regression presented a higher gradient in the redistribution Tl-201 radioactivity between the chronic and acute/subacute images than those without Q-wave regression. CONCLUSIONS: This study supports the role of functional recovery of stunning and/or hibernating myocardium in the disappearance of Q waves after AMI.     

Left ventricular dyssynchrony assessed by two three-dimensional imaging modalities: phase analysis of gated myocardial perfusion SPECT and tri-plane tissue Doppler imaging

Purpose To compare left ventricular (LV) dyssynchrony assessment by phase analysis from gated myocardial perfusion SPECT (GMPS) with LV dyssynchrony assessment by tri-plane tissue Doppler imaging (TDI). Baseline LV dyssynchrony assessed with standard deviation (SD) of time-to-peak systolic velocity of 12 LV segments (Ts-SD) with TDI has proven to be a powerful predictor of response to CRT. Information on LV dyssynchrony can also be provided by GMPS with phase analysis of regional LV maximal count changes throughout the cardiac cycle. Methods Forty heart failure patients, referred for evaluation of potential eligibility for CRT, underwent both 3D echocardiography, with tri-plane TDI, and resting GMPS. From tri-plane TDI, Ts-SD was used as a validated parameter of LV dyssynchrony and compared with different indices (histogram bandwidth, phase SD, histogram skewness and kurtosis) derived from phase analysis of GMPS. Results Histogram bandwidth and phase SD showed good correlation with Ts-SD (r=0.77 and r=0.74, p<0.0001, respectively). Patients with substantial LV dyssynchrony assessed with tri-plane TDI (Ts-SD ≥33 ms) had also significantly higher values of histogram bandwidth and phase SD. Conclusions The results of this study support the use of phase analysis by GMPS to evaluate LV dyssynchrony. Histogram bandwidth and phase SD showed the best correlation with Ts-SD assessed with tri-plane TDI and appeared the most optimal variables for assessment of LV dyssynchrony with GMPS.     

Serial cine-magnetic resonance imaging of left ventricular remodeling after myocardial infarction in rats.

The purpose of the present study was the serial investigation of morphological and functional changes after left coronary artery ligation in the intact rat using cine-magnetic resonance imaging (MRI). MRI studies were performed 4, 8, 12, and 16 weeks after myocardial infarction (MI) with an echocardiogram (ECG)-triggered cine-fast low-angle shot (FLASH)-sequence in a 7-Tesla magnet. MI-size, left ventricular (LV) mass and volumes, cardiac index, ejection fraction (EF), and remote wall and scar thickness of 11 Wistar rats were compared to four sham-operated rats. Stress MRI with dobutamine (10 microl/kg x minute) was performed at 16 weeks. In MI groups (small MI < 30%, N = 5, large MI > 30%, N = 6), there was significant increase of LV mass (small MI + 47.8% increase, large MI + 74.1%) and wall thickness (large MI 1.21 +/- 0.03 to 1.84 +/- 0.07 mm). Scar thickness declined from four to 16 weeks (large MI 0.92 +/- 0.06 to 0.38 +/- 0.02 mm, P < 0.05). End-diastolic volume of both MI groups was significantly elevated but increased further only in animals with large MI from four to 16 weeks (657.1 +/- 38.6 to 869.7 +/- 60.7 microL, P < 0.05). Compared to sham, EF was significantly depressed in MI (large MI 31.5 +/- 2.0%). Wall thickening declined from four to 16 weeks post-MI (large MI 50.9 +/- 9.9 to 28.9 +/- 4.4%, P < 0.05). During stress, sham and MI rats increased wall thickening from 66.5 +/- 8.2 to 111.2 +/- 6.7% and from 30.8 +/- 4.3 to 47.5 +/- 5.8%, respectively (P < 0.05). Hypertrophy was found in all animals with MI throughout the entire period of observation, whereas dilatation after four weeks was only detected in animals with large MI. These morphologic changes were accompanied by an early decline of EF; myocardial function characterized by wall thickening deteriorated later.     

高血压病心肌灌注及硝酸甘油介入显像与室性心律失常关系的研究

目的　探讨高血压病心肌显像异常的临床意义及与心律失常的关系。方法　对 88例高血压患者行99Tcm 甲氧基异丁基异腈心肌灌注断层显像 ,对其中 5 7例显像异常者再行硝酸甘油介入心肌显像。所有患者均行Holter检查 ,冠状动脉造影 31例。结果　运动和静息显像后仍有 6 4 8%患者灌注减低 ,6 0 2 %的灌注减低节段硝酸甘油介入显示有填充或不完全填充 ,提示合并冠心病。多因素逐步回归分析表明 ,室性心律失常与心肌灌注减低的程度及左室肥厚 (LVH)呈线性回归关系。结论　心肌灌注断层显像及硝酸甘油介入心肌显像能反映高血压患者是否合并冠心病 ,并与其他高血压性病理改变所致的灌注减低相区别。高血压合并冠心病及LVH是心律失常的重要病理基础。