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

Journal of Nuclear Cardiology -     

Myocardial fibrosis detected by cardiac CT predicts ventricular fibrillation/ventricular tachycardia events in patients with hypertrophic cardiomyopathy

BackgroundMyocardial fibrosis (MF) occurs in up to 80% of subjects with asymptomatic or mildly symptomatic hypertrophic cardiomyopathy (HCM) and can constitute an arrhythmogenic substrate for re-entrant, life-threatening ventricular arrhythmias in predisposed persons.ObjectiveThe aim was to investigate whether MF detected by delayed enhancement cardiac CT is predictive of ventricular tachycardia (VT) and fibrillation (VF) that require appropriate therapy by an implantable cardioverter defibrillator (ICD) in patients with HCM.MethodsTwenty-six patients with HCM with previously (for at least 1 year) implanted ICD underwent MF evaluation by cardiac CT. MF was quantified by myocardial delayed enhanced cardiac CT. Data on ICD firing were recorded every 3 months after ICD implantation. Risk factors for sudden cardiac death in patients with HCM were evaluated in all patients.ResultsMF was present in 25 of 26 patients (96%) with mean fibrosis mass of 20.5 ± 15.8 g. Patients with appropriate ICD shocks for VF/VT had significantly greater MF mass than patients without (29.10 ± 19.13 g vs 13.57 ± 8.31 g; P = .01). For a MF mass of at least 18 g, sensitivity and specificity for appropriate ICD firing were 73% (95% CI, 49%–88%) and 71% (95% CI, 56%–81%), respectively. Kaplan–Meier curves indicated a significantly greater VF/VT event rate in patients with MF mass ≥18 g than in patients with MF <18 g (P = .02). In the Cox regression analysis, the amount of MF was independently associated with VF/VT in ICD-stored electrograms.ConclusionThe mass of MF detected by cardiac CT in patients with HCM at high risk of sudden death was associated with appropriate ICD firings.     

Prevalence of cerebral microhemorrhages in amateur boxers as detected by 3T MR imaging

BACKGROUND AND PURPOSE: The evidence for traumatic brain injury in amateur boxers is controversial. Hypothetically, sudden acceleration of the head due to the impact of the blow during the boxing fight might result in diffuse axonal injury or contusion. We wanted to determine whether cerebral microhemorrhages occur more often in amateur boxers than in nonboxers.MATERIALS AND METHODS: In 42 male, classical amateur boxers and in 37 healthy, nonboxing male volunteers we performed cranial MR imaging at 3T. The study protocol included a transverse dual spin-echo MR imaging sequence, a 3D sagittal magnetization-prepared rapid acquisition of gradient echo sequence, a coronal T2*-weighted sequence, and an axial time-of-flight MR angiography sequence. MR imaging data were made anonymous before 2 neuroradiologists independently evaluated the images. In addition, the following risk factors were assessed: total numbers of fights and knockouts, weight division, and duration of boxing. We compared the group proportions of microhemorrhages with Fisher test of exact probability.RESULTS: There was a statistically higher prevalence of cerebral microhemorrhages in the group of boxers (3 of 42; 7.1%) than in nonboxing persons (0 of 37; 0%). This difference was not statistically significant, however (P = .2479; Fisher exact test).CONCLUSION: Although we detected more microhemorrhages in amateur boxers than in nonboxing persons, this difference did not prove to be significant.

Hypothetically, sudden acceleration of the head because of the impact of a blow during a boxing fight might result in cerebral contusion involving the superficial gray matter, in diffuse axonal injury (DAI) from axonal stretching because of a movement of the overlying cerebral cortex relative to the underlying cerebral white matter, or in subcortical injury. DAI can be detected by MR imaging as multiple round or ovoid lesions of the cerebral white matter, especially at the gray/white matter interface (corticomedullary junction), the corpus callosum, and the upper brain stem, representing multifocal punctate hemorrhages. T2*- and susceptibility-weighted gradient-echo images are very useful tools for detecting small foci of hemorrhage in the brain. An additional increase in the sensitivity for detecting hemorrhagic shear injuries can be achieved using higher MR field strengths, such as 3T.¹ Because the evidence concerning traumatic brain injury in amateur boxers is controversial,^2–6 the aim of our study was to determine the prevalence of cerebral microhemorrhages in boxers as compared with nonboxers by using 3T MR imaging. Our working hypothesis was that MR imaging would show a higher prevalence of cerebral microhemorrhages in amateur boxers than in nonboxers.     

Variation of lateral ventricular volume during the cardiac cycle observed by MR imaging

CSF pulsation suggests variation in the size of the cerebral ventricles during the cardiac cycle. The arterial blood flow and venous outflow are two major components that contribute to the variation. High-resolution MR imaging with cardiac gating provides sharp delineation of the cerebral ventricles with clear boundaries. Subtle changes in the size of the ventricles during the cardiac cycle are measurable with high precision and accuracy by using a sophisticated automated edge-detection algorithm. In 12 normal individuals, the cerebral ventricles were examined, and the size of the lateral ventricles showed a 10-20% change during the cardiac cycle. The pattern is complex but similar in appearance to the intracranial pressure pulse waveform. The variation suggests that the choroid plexus may play a greater role as a source of CSF pulsation that currently acknowledged. The ability to measure the variations in ventricular volume has clinical implication as a noninvasive method for the diagnosis of diseases with abnormal brain elasticity.     

Improved labelling of no-carrier-added 123I-MIBG and preliminary clinical evaluation in patients with ventricular arrhythmias.

Meta-[123I]iodobenzylguanidine (123I-MIBG) is currently used to assess myocardial sympathetic innervation by single photon emission tomography (SPET). In recent studies, an enhanced cardiac uptake of 123I-MIBG with high specific activity has been reported, suggesting the clinical potential of no-carrier-added (n.c.a.) 123I-MIBG in the assessment of abnormalities in cardiac sympathetic function. This paper describes the preparation of n.c.a. 123I-MIBG by non-isotopic Cu(I)-assisted [123I]iododebromination and by [123I]iododestannylation, both resulting in n.c.a. 123I-MIBG with radiochemical yields of 88 +/- 6% and high specific activity (> or = 6.3 TBq.mumol-1) in a total synthesis time of less than 50 min. The diagnostic potential of n.c.a. 123I-MIBG (> 6.3 TBq.mumol-1) was studied in 13 patients (nine patients with malignant ventricular arrhythmias and four patients suspected of phaeochromocytoma) and compared to commercial 123I-MIBG (approximately 75 MBq.mumol-1) using a dual-headed SPET camera (MULTISPECT II). High specific activity results in higher 123I-MIBG uptake in the heart and in the liver in all patients. The calculated heart-to-lung and heart-to-liver count ratios 4.5 h post-injection increased by 22 +/- 6% and 10 +/- 5% with n.c.a. 123I-MIBG compared to commercial 123I-MIBG respectively. In contrast, no significant correlation between the specific activity of 123I-MIBG and lung uptake could be established in this study. Analysis of radioactivity in blood after the intravenous injection of n.c.a. and commercially available 123I-MIBG showed an initial rapid clearance of radioactivity from blood, followed by a plateau from 60 min onwards. Within the first 24 h, more than 85% of the plasma activity was unchanged 123I-MIBG. The free 123I-iodide concentration determined 24 h post-injection was 2 +/- 1% with commercial 123I-MIBG and 3 +/- 2% with n.c.a. 123I-MIBG. In conclusion, the results of this investigation indicate that n.c.a. 123I-MIBG is a promising clinical tool for imaging myocardial sympathetic dysfunction by SPET. High specific activity n.c.a. 123I-MIBG can now be prepared by simple one-step methods giving high radiochemical yields and high purity suitable for clinical application. This encourages the further clinical validation of n.c.a. 123I-MIBG on a large scale.     

Details of left ventricular radial wall motion supporting the ventricular theory of the third heart sound obtained by cardiac MR

Objective:

Obtaining new details of radial motion of left ventricular (LV) segments using velocity-encoding cardiac MRI.

Methods:

Cardiac MR examinations were performed on 14 healthy volunteers aged between 19 and 26 years. Cine images for navigator-gated phase contrast velocity mapping were acquired using a black blood segmented κ-space spoiled gradient echo sequence with a temporal resolution of 13.8 ms. Peak systolic and diastolic radial velocities as well as radial velocity curves were obtained for 16 ventricular segments.

Results:

Significant differences among peak radial velocities of basal and mid-ventricular segments have been recorded. Particular patterns of segmental radial velocity curves were also noted. An additional wave of outward radial movement during the phase of rapid ventricular filling, corresponding to the expected timing of the third heart sound, appeared of particular interest.

Conclusion:

The technique has allowed visualization of new details of LV radial wall motion. In particular, higher peak systolic radial velocities of anterior and inferior segments are suggestive of a relatively higher dynamics of anteroposterior vs lateral radial motion in systole. Specific patterns of radial motion of other LV segments may provide additional insights into LV mechanics.

Advances in knowledge:

The outward radial movement of LV segments impacted by the blood flow during rapid ventricular filling provides a potential substrate for the third heart sound. A biphasic radial expansion of the basal anteroseptal segment in early diastole is likely to be related to the simultaneous longitudinal LV displacement by the stretched great vessels following repolarization and their close apposition to this segment.Advances in cardiac imaging techniques have allowed evaluation of new details of the complex pattern of left ventricular (LV) motion. Using high temporal resolution cardiovascular MR with myocardial velocity-encoding techniques, we previously performed a detailed analysis of rotational and longitudinal motions of the left ventricle, correlating them with the orientation or cardiomyocyte aggregates within the LV wall.^1,2 However, accurate evaluation of radial motion is equally important. For example, radial wall motion abnormalities have been detected in patients with diabetes³ and hypertrophic cardiomyopathy,⁴ whereas radial dyssynchrony is almost universal in patients with heart failure.⁵ The purpose of this study was to obtain new details of global and regional radial wall motion of the left ventricle using the cardiac MR high temporal resolution myocardial velocity-encoding technique.^6,7 Considering recent interest in myocardial multilayer measurements, which provide more layer-specific information about the functional state of the myocardium at different levels,^8–13 separate calculations of all myocardial velocities and their corresponding peak times for the inner (endocardial), middle (transmural) and outer (epicardial) layers of the LV wall were performed.     

CT features of myocardial fat and correlation with clinical background in patients without cardiac disease

Objective

To evaluate the frequency and common locations of myocardial fat and its associated factors using coronary CT angiography (CCTA) in patients without cardiac disease.

Methods

Using CCTA findings for 298 consecutive patients without cardiac disease, we categorized the myocardium into nine locations, scored fat in those locations, and correlated the fat score with the thickness of the right ventricular (RV) free wall and factors including gender, age, and body mass index (BMI) as well as history of diabetes mellitus, hypertension (HT), and dyslipidemia.

Results

We observed myocardial fat in 68.5 % of patients, most commonly in the RV outflow tract (RVOT, 64.1 %), followed by the base (42.3 %) and middle (28.9 %) of the RV free wall, RV trabeculations (22.5 %), and the left ventricular apex (11.4 %). The RV free wall thickened significantly with increasing fat score. Dependent variables for myocardial fat were female gender (P < 0.0001), age ≥65 years (P = 0.0043), BMI ≥25 (P = 0.0050), and HT (P = 0.0139).

Conclusion

Myocardial fat is a common finding on CCTA in patients without cardiac disease, is often observed in the RVOT, and is more frequent in female patients, those older than 65 years, those with BMI ≥25, and those with HT.     

The relevance of free fluid between intestinal loops detected by sonography in the clinical assessment of small bowel obstruction in adults

INTRODUCTION: The main role of the radiologist in the management of patients with suspicion of small bowel obstruction is to help triage patients into those that need immediate surgical intervention from those that require medical therapy or delayed surgery. Ultrasound examination is usually considered not helpful in bowel obstruction because of air in the intestinal lumen that interferes the evaluation of the intestinal loops, however recently some Authors attested the increasing important role of sonography in the acute abdominal disease. Aim of our report is to demonstrate the value of free fluid detected by US in differentiating between low and high-grade small bowel obstruction. MATERIALS AND METHODS: The study is based on 742 consecutive patients who presented symptoms of the acute abdomen; all patients had undergone initial serial abdominal plain film and US examinations prior to any medical intervention. We reviewed the imaging findings of 150 cases in whom small bowel obstruction was clinically suspected and confirmed at surgery. We consider the following radiographic and US findings: dilatation of small bowel loops; bowel wall thickness; presence of air-fluid levels; thickness of valvulae conniventes; evidence of peristalsis; presence and echogenicity of extraluminal fluid. We looked at the value of extraluminal peritoneal fluid at US examination in differentiating low and high-grade small bowel obstruction based on the surgical outcome. RESULTS: In 46 patients altered peristaltic activity, thin bowel walls, fluid filled loops with hyperechoic spots in the bowel segment proximal to obstruction were noted at US, whereas radiographic features were: moderate dilatation of small bowel loops, with thin bowel wall and evidence of numerous and subtle valvulae conniventes; presence of air-fluid levels was also noted. In 70 other patients, US examination revealed all the findings described in the precedent cases and also the presence of free extraluminal fluid; abdominal plain film showed an increased dilatation of small bowel loops with moderate thickened wall and air-fluid levels. In 34 other patients US examination revealed the presence of thick-walled loops, hypoperistalsis and a larger amount of free extraluminal fluid. Radiographic findings in these patients were: horizontal featured and markedly dilated small bowel loops presenting parietal thickness, presence of intraluminal fluid stasis and evidence of thickened, sparse and incomplete valvulae conniventes. At surgery etiology of small bowel obstructions was various, but most of cases related to adhesions (70 cases). The presence of extraluminal fluid were confirmed at surgery in 104 patients. CONCLUSIONS: Our experience using sonography in suspicion of SBO (small bowel obstruction) suggests the usefulness of this imaging modality to differentiate a functional or obstructive ileus, demonstrating the evidence of intestinal peristalsis. Furthermore, the presence of a large amount of fluid between dilated small bowel loops suggests worsening mechanical small bowel obstruction, that requires not a medical therapy but immediate surgery.     

心血管MR在诊断左心室非填塞性心肌病及其他心肌病的鉴别中的价值

目的评价心血管MR(CMR)所获得的心肌参数对于鉴别左心室非填塞性心肌病(LVNC)与其他类型心肌病及对照组的价值。方法回顾性分析12例LVNC,11例扩张性心肌病,10例肥厚性心肌病,并且与24例正常对照相比较。所有的LVNC病人均符合经典的超声心动图以及其他临床和影像诊断标准。采集稳态自由进动电影序列和延迟钆增强图像。计算全部的左心室心肌质量指数(LV-MMI)、填塞部分的左心室心肌质量指数(LV-MMI填塞)、非填塞部分的左心室心肌质量指数(LV-MMI非填塞)、非填塞部分的左心室心肌质量(LV-MM非填塞)百分比,以及心室容积和功能。采用方差分析和Dunnett检验进行统计学分析。此外,采用对各心室段的小梁形成增加进行半定量分析。结果 LV-MMI非填塞和LV-MM非填塞百分比是区分LVNC、健康对照组和其他类型心肌病之间的敏感指标,临界值分别为15g/m2和25%。并且,心底部的小梁形成和非填塞/填塞心肌的比率≥3:1是LVNC的诊断标准。这些标准联合应用可将诊断的敏感度和特异度提升到100%。所有的LVNC病人均未出现延迟强化。结论心血管MR定量分析的LV-MMI非填塞和LV-MM非填塞百分比和基底段的小梁形成增加能够可靠地诊断LVNC,并可与其他类型的心肌病进行鉴别。     

Value of cardiovascular MR in diagnosing left ventricular non-compaction cardiomyopathy and in discriminating between other cardiomyopathies

Objectives

To analyse the value of cardiovascular magnetic resonance (CMR)-derived myocardial parameters to differentiate left ventricular non-compaction cardiomyopathy (LVNC) from other cardiomyopathies and controls.

Methods

We retrospectively analysed 12 patients with LVNC, 11 with dilated and 10 with hypertrophic cardiomyopathy and compared them to 24 controls. LVNC patients had to fulfil standard echocardiographic criteria as well as additional clinical and imaging criteria. Cine steady-state free precession and late gadolinium enhancement (LGE) imaging was performed. The total LV myocardial mass index (LV-MMI), compacted (LV-MMI_compacted), non-compacted (LV-MMI_{non-compacted}), percentage LV-MM_{non-compacted}, ventricular volumes and function were calculated. Data were compared using analysis of variance and Dunnett’s test. Additionally, semi-quantitative segmental analyses of the occurrence of increased trabeculation were performed.

Results

Total LV-MMI_{non-compacted} and percentage LV-MM_{non-compacted} were discriminators between patients with LVCN, healthy controls and those with other cardiomyopathies with cut-offs of 15?g/m² and 25?%, respectively. Furthermore, trabeculation in basal segments and a ratio of non-compacted/compacted myocardium of ≥3:1 were criteria for LVNC. A combination of these criteria provided sensitivities and specificities of up to 100?%. None of the LVNC patients demonstrated LGE.

Conclusions

Absolute CMR quantification of the LV-MMI_{non-compacted} or the percentage LV-MM_{non-compacted} and increased trabeculation in basal segments allows one to reliably diagnose LVNC and to differentiate it from other cardiomyopathies.

Key Points

? Cardiac magnetic resonance imaging can reliably diagnose left ventricular non-compaction cardiomyopathy. ? Differentiation of LVNC from other cardiomyopathies and normal hearts is possible. ? The best diagnostic performance can be achieved if combined MRI criteria for the diagnosis are used.     

Regional myocardial damage and active inflammation in patients with cardiac sarcoidosis detected by non-invasive multi-modal imaging

Aims

Cardiac sarcoidosis (CS) can be diagnosed using ¹⁸F-FDG-PET/CT (PET), cardiovascular magnetic resonance (CMR), and ¹²³I-BMIPP/²⁰¹TlCl dual myocardial SPECT. This study aims to clarify the relationships among the three modalities with respect to CS.

Methods and results

We evaluated 16 patients (male n = 11; age 55 ± 13 years) with confirmed CS who underwent PET, CMR, and dual SPECT with gated SPECT before starting steroid therapy. The left ventricular myocardium was divided into 17 segments to obtain SUVmax for PET images, defect scores from 0 to 4 (0 normal; 4 absent), and mismatch scores for dual SPECT (BMDS, TLDS, and MS) images and late gadolinium enhancement (LGE) scores (0 none; 1 partly positive; 2 homogeneous) on CMR images. Summed BMDS, TLDS, and MS were 18.6 ± 12.6, 12.9 ± 10.9, and 5.7 ± 3.1, respectively. The segmental BMDS and TLDS scores became significantly higher as the LGE scores increased. The MS scores were significantly higher in areas of LGE with a score of 1 than 0 (both, p < 0.001), but did not significantly differ between areas with LGE scores of 1 and 2. The SUVmax was significantly higher in LGE areas with a score of 1 than 0 (p < 0.025), but did not significantly differ between those with scores of 1 or 2.

Conclusion

Regions with a higher SUVmax indicating active myocardial inflammation were mainly located in areas with LGE, where BMIPP and TL mismatches were evident in patients with CS.

     

Changes in left and right ventricular cardiac function after valve replacement for aortic stenosis determined by cine MR imaging

The purpose of this study was to determine the changes in function of both the left and the right ventricles (LV, RV) before and after aortic valve replacement (AVR), compared with age-matched healthy volunteers using magnetic resonance (MR) imaging. Fourteen patients with aortic stenosis underwent MR imaging (1.5 T) before and 3 (n = 14) and 12 (n = 9) months after surgical valve replacement. An electrocardiographically triggered two-dimensional cine fast low-angle shot sequence was used for the evaluation of absolute values and indices related to 1 m(2) body surface area for function, mass, and LV wall thickening. Fourteen age-matched healthy volunteers served as controls. Before surgery, all patients showed significant abnormalities of LV mass and function, whereas RV mass and function were not different from those of volunteers and remained mostly unchanged. After surgery, normalization of LV ejection fraction, absolute mass, and end-systolic wall thickness was observed, whereas the LV mass index failed to normalize, and LV volumes remained elevated. Aortic stenosis combined with a significant, but not severe reduction in LV function only affects the LV, whereas the RV remains unaffected at this stage of disease. AVR leads to improved LV function and reduced hypertrophy, but without normalization of LV volumes or the LV mass index within 1 year.     

Myocardial defect detected by123I-BMIPP scintigraphy and left ventricular dysfunction in patients with idiopathic dilated cardiomyopathy

The present study examined the role of myocardial fatty acid in patients with idiopathic cardiomyopathy (DCM) by means of¹²³I-β-methyl-p-iodophenyl pentadecanoic acid (¹²³I-BMIPP) scintigraphy. Thirteen patients underwent¹²³I-BMIPP imaging,²⁰¹Tl imaging and echocardiography. All patients showed defective myocardial uptake of¹²³I-BMIPP and²⁰¹Tl. The left ventricular end-diastolic dimension (64.1 ± 7.3 mm vs. 55.6 ± 1.5 mm, p < 0.05) and end-systolic dimension (52.4 ± 8.0 mm vs. 40.6 ± 2.1 mm, p < 0.01) were significantly larger in the large defect group (¹²³I-BMIPP defect score (DS) > 8) than the small defect group (DS < 7). The % fractional shortening (%FS) was also significantly smaller (18.6 ± 3.8% vs. 27.0 ± 3.3%, p < 0.01) in the large defect group. The¹²³I-BMIPP DS correlated statistically with %FS (r = 0.75, p < 0.01), while the²⁰¹Tl DS did not (r = 0.41, ns). We conclude that the patients with DCM revealed a¹²³I-BMIPP uptake defect and the defect reflected the degree of left ventricular dysfunction.