M. Lombardi

Myocardial Structural, Perfusion, and Metabolic Correlates of Left Bundle Branch Block Mechanical Derangement in Patients With Dilated Cardiomyopathy A Tagged Cardiac Magnetic Resonance and Positron Emission Tomography Study

Background—Left bundle branch block (LBBB) influences on regional left ventricular (LV) structure, perfusion, and metabolism have not yet been thoroughly investigated in dilated cardiomyopathy patients. Methods and Results—Eleven dilated cardiomyopathy patients with LBBB (mean±SD age, 62±11 years; LV ejection fraction, 35±8%) and 7 dilated cardiomyopathy patients without LBBB (mean±SD age, 58±9 years; LV ejection fraction, 37±10%) were studied by cardiac magnetic resonance and positron emission tomography. The left ventricle was divided in 3 regions: septum, adjacent (anterior-inferior walls), and lateral. Regional midwall circumferential strain, maximum shortening, and strain rate were obtained from tagged cardiac magnetic resonance. The systolic stretch index was calculated as positive strain rate (stretching) divided by total strain rate. Myocardial metabolic rate of glucose and resting and hyperemic myocardial blood flow were quantified by 2-[18F]fluoro-2-deoxyglucose and [13N]ammonia positron emission tomography, respectively. Compared with non-LBBB patients, LBBB patients showed a highly inhomogeneous systolic deformation pattern that changed gradually, moving from a discoordinate [(systolic stretch index, 0.485 (0.284)] and poorly contracting (maximum shortening, −1.14±0.96%) septum to a coordinate [systolic stretch index, 0.002 (0.168)] and strongly contracting (maximum shortening, −13.63±2.58%) lateral region (both P<0.0001). This pattern was closely matched to the myocardial metabolic rate of glucose, disclosing lowest, intermediate, and highest values in the septum, adjacent, and lateral regions, respectively (P<0.0001). Septal-to-lateral thickness ratio was lower in LBBB than in non-LBBB patients (P=0.03). In both groups, the LV distribution of resting and hyperemic myocardial blood flow and myocardial blood flow reserve did not differ significantly. Conclusions—In dilated cardiomyopathy patients, the extensive LV contraction abnormalities induced by LBBB cause regional myocardial metabolic and structural remodeling, without consistent changes in blood flow.

Myocardial perfusion by first pass contrast magnetic resonance: a robust method for quantitative regional assessment of perfusion reserve index

Assessing myocardial perfusion is a key issue in the diagnosis and subsequent treatment of patients with coronary artery disease (CAD).1,2 A single magnetic resonance (MR) examination can assess perfusion by monitoring the upslope of the signal change in dependence on the first pass of gadolinium derivatives. We propose a method of evaluating the regional distribution of the perfusion reserve index (PRI), defined as the ratio between stress and resting upslopes. The PRI regional distribution was assessed in patients with and without CAD and a PRI cut off was identified.nnThirty two patients (mean (SD) age 65 (10) years, 20 men) underwent MR imaging and quantitative coronary angiography to assess the presence of coronary artery stenoses. The protocol was approved by the institutional ethics committees and informed consent was obtained from all patients.nnMR images were acquired with a GE Signa 1.5 T scanner during gadolinium-diethylenetriaminepentaacetic acid (DTPA) infusion (Omniscan, Nycomed Imaging, Roskilde, Denmark) into a cubital vein (0.1 mmol/kg, 5 ml/s) followed by 10 ml of saline flush. A cardiac array coil was used, with fast gradient echo with an echo train readout sequence. For each examination, three 256 × 256 short axis slices (basal, middle, and distal) were acquired in the diastolic phase during an RR interval with a slice thickness of 8 mm. The acquisition was repeated along 60 RR intervals. All the patients were asked to hold their …

Quantitative 3D assessment of myocardial viability with MRI delayed contrast enhancement

Myocardial viability is a fundamental question in the clinical and therapeutic decision making process. Contrast-enhanced MRI can distinguish between viable and necrotic myocardium in non-invasive manner and with excellent definition of endocardial and epicardial borders. Aim of this study is to propose a software methodology that allows to assess the global, transmural and intramural extent of myocardial necrosis providing both bull-eyes and 3D representation of contrast delayed enhanced area in MRI cardiac images.

MYOCARDIAL GADOLINIUM KINETICS EVALUATION AT MRI FOR THE DIAGNOSIS OF CARDIAC AMYLOIDOSIS

Late Gadolinium Enhancement (LGE) technique is currently used for the diagnosis of Cardiac Amyloidosis (CA) by Magnetic Resonance (MRI). However, LGE pattern lacks of sensitivity because it is absent in 30% of patients with CA in previous series.nnTo test a new method for diagnosis of CA by the

Computerized radio-frequency analysis of concentration and 'decay' of echo-contrast agents

The linear relationship between dose of contrast agent and radio-frequency (RF) signal constitutes a means of noninvasive evaluation of intracardiac flows by contrast echocardiography. To assess the concentration of echo-contrast agents by ultrasound, a commercially available echocardiographic instrument was modified. The RF signal (unprocessed backscattered signal) corresponding to a region of interest inside the 2-D echo image was sampled in real time and transferred online to a personal computer. The relationship between different doses of contrast agent and RF signal was tested in an in vitro system of circulation. In the range of doses between 0.25 and 1.5 ml of contrast a linear correlation was found between dose and RF (r=0.92). At higher doses (1.75-2.0) ml, the dynamic converter used in this modified echo instrument produced a significant distortion of the signal. The system also made it possible to study the spontaneous decay of the echo contrast agent. The spontaneous T/sub 1/2/ (68 s) is long enough to allow flow evaluation.<<ETX>>

CMR survey in a large cohort of TI patients categorized in different transfusional regimens

Purpose: We investigated myocardial iron overload (MIO), biventricular parameters and myocardial fibrosis assessed by cardiovascular magnetic resonance (CMR) in a large cohort of thalassemia intermedia (TI) patients categorized in different transfusional regimens. This survey is particularly significant considering the debate on the opportunity to transfuse the TI patients.nnMethods: We studied retrospectively 252 adult TI patients (119 females, 39±10 yrs) enrolled in the MIOT Network. MIO was assessed by a multislice multiecho T2* approach. Cine sequences were obtained to quantify biventricular function parameters. Myocardial fibrosis was evaluated by late gadolinium enhancement (LGE) acquisitions.nnResults: 188 patients showed no MIO in any segment, 56 had an heterogeneous MIO (52 with a global heart T2*<20 ms), and 8 showed an homogeneous MIO.nnLeft ventricular (LV) and right ventricular (RV) dilatations were present in the 45% and in the 19% of cases, respectively. LV dysfunction was present in the 18.0% of the cases while RV dysfunction in the 3.63%. LV hypertrophy was found in the 8.7% of cases.nnMyocardial fibrosis was found in the 22.9% of the patients and was associated with LV dysfunction (P=0.001) and hypertrophy (P=0.038).nn48 patients were no transfused, 66 sporadically transfused and 138 regularly transfused. The 3 group were significantly different for the LV volume and mass indexes, the cardiac output and the myocardial fibrosis (Table).nnView this table:nnnnConclusions: Heart iron was not absent in TI and the majority of the patients showed an heterogeneous distribution. A consistent number of the TI patients had the stigmata of the high cardiac output state cardiomyopathy and myocardial fibrosis seems to be related to the high cardiac output state. The signs of the high cardiac output state were controlled in the regular transfused patients. Conversely, the regular transfusions seem to be started too late for preventing myocardial fibrosis.

Frequency domain analysis of contrast echocardiographic images

Sequences of echocontrastographic images of the dogs myocardium are analysed in the frequency domain for the identification of underperfused areas. Owing to the fact that echo images are contaminated by noise and artifacts, we have applied filtering techniques based on Fouriers methods in sequences of raw frames recorded during perfusion with a contrast agent. Thus we have been able to assess correctly the spatial and temporal distribution of the contrast, i.e. the agent kinetics which parallel the distribution of coronary blood flow, in terms of the time necessary for the flow gradient to reach its maximum value, and to describe such a distribution by a functional image obtained by means of an original procedure.