Evaluation of left ventricular volumes measured by magnetic resonance imaging

Left ventricular end-diastolic and end-systolic volumes were determined in 17 patients with different levels of left ventricular function by magnetic resonance imaging (MRI). A 1.5 Tesla Magnet was used obtaining ECG triggered single and multiple slices. Calculated cardiac outputs were compared with those measured simultaneously by a classical physiological indicator dilution technique. There was good agreement between cardiac output as measured by MRI and the indicator dilution method, when the multislice technique was used (r = 0.87, p less than 0.001). A poor correlation between the two methods was seen when the single slice technique was used (r = 0.06, p greater than 0.80). The results indicate that MRI is a reliable method for left ventricular volume determination when the multislice technique is used.     

Left ventricular volume measured rapidly by oblique magnetic resonance imaging

Magnetic resonance measurements of left ventricular volume and ejection fraction based on measurements of area and length in a single oblique plane containing the long axis of the ventricle were compared with measurements made by summing the areas of the chamber in multiple contiguous slices. The multislice technique is known to be accurate, but the single slice technique is much quicker; it takes only nine minutes of acquisition time for both volume and ejection fraction. In 25 normal subjects there was good agreement between the two methods of measuring volume with a mean (SD) difference between measurements of 2.0 (6.6) ml. In 20 patients with previous infarction it was less good with a mean (SD) difference of 4.5 (18.1) ml. The mean (SD) difference of ejection fraction measurements was -0.019 (0.038) in the normal subjects and -0.059 (0.106) in the patients, and the discrepancy between the two techniques was greatest in the patients with a pronounced abnormality of wall motion and low ejection fraction. In a further 25 normal subjects, the agreement between single plane volume measurements in the vertical and horizontal long axis planes was good, indicating that either plane is suitable for rapid measurement. Single plane measurements of left ventricular volume and ejection fraction can be made with the accuracies stated, which are sufficient for routine clinical use except in patients with a pronounced abnormality of wall motion. In combination with measurements of regional wall thickness and motion, previously described, the technique offers a rapid non-invasive assessment of both global and regional left ventricular function.     

Evaluation of the right ventricle by magnetic resonance imaging

The ability of magnetic resonance imaging to evaluate right ventricular architecture and size was assessed in 149 subjects (26 normal volunteers and 123 patients with heart disease). The right ventricular myocardium was clearly delineated from adjacent structures in all patients. The trabeculated pattern of the right ventricle was well seen and was most evident during systole and in patients with right ventricular hypertrophy. The moderator band was discernible in 72% of the subjects, whereas smaller muscular structures such as the papillary muscles were identified less frequently. Magnetic resonance imaging provided a good image of the tricuspid valve leaflets but did not show the pulmonic leaflets well. The clear visualization of the endocardial and epicardial borders obtained with magnetic resonance imaging allowed measurement of wall thickness and of the internal dimensions of the cavity in normal subjects, in patients with moderate to severe systolic overload, and in patients with moderate to severe diastolic overload. Patients with severe systolic overload of the right ventricle had markedly thicker walls when compared with patients without this condition. The mean internal dimension at end diastole of patients with severe diastolic overload of the right ventricle was significantly increased when compared to other subgroups. Magnetic resonance imaging provides tomographic images of the right ventricle with clear distinction of the endocardial and epicardial surfaces that can be useful for quantitative and qualitative assessment of this complex structure.     

Measurement of ventricular volumes in the dog by nuclear magnetic resonance imaging

Nuclear magnetic resonance (NMR) imaging is a new, noninvasive approach for imaging the cardiovascular system. Being a three-dimensional technique, NMR imaging has the capability of measuring volumes without the need for assumptions regarding ventricular geometry. In this study, the technique was validated in 19 excised dog hearts, filled with silicone-rubber, imaged using a multislice spin-echo sequence. The volume of the cavity in each slice was calculated from the number of pixels outlined for each slice multiplied by the pixel volume. Ventricular volumes measured by NMR imaging were highly correlated with cast volumes measured by water displacement: right ventricle (RV):RVNMR = 1.05 RVcast - 1.62; r = 0.99, SEE = 0.96 ml; left ventricle (LV):LVNMR = 0.98 LVcast + 0.35, r = 0.98, SEE = 1.48 ml. After validation in casts, NMR imaging volumes were measured in eight living dogs using a multiphasic gated technique to obtain images at 5, 105, 205, 305 and 405 ms after the QRS complex. Cardiac output (CO) and stroke volume (SV) measured by NMR imaging were significantly correlated with thermodilution (TD) measurements (CONMR = 0.63 COTD + 0.51 liters/min; r = 0.78, SEE = 0.57 liters/min; SVNMR = 0.67 SVTD + 1.95 ml; SEE = 5.58 ml). Right and left stroke volumes were closely related (LVSVNMR = 0.9 RVSVNMR + 1.75; r = 0.94, SEE = 4.32 ml), with the slope and intercept of the regression line showing no difference from 1 and 0, respectively. However, volumes determined by NMR imaging underestimated the thermodilution measurements, presumably reflecting the inability to obtain a true systolic image with the present sampling rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Left ventricular volume measured rapidly by oblique magnetic resonance imaging.

Magnetic resonance measurements of left ventricular volume and ejection fraction based on measurements of area and length in a single oblique plane containing the long axis of the ventricle were compared with measurements made by summing the areas of the chamber in multiple contiguous slices. The multislice technique is known to be accurate, but the single slice technique is much quicker; it takes only nine minutes of acquisition time for both volume and ejection fraction. In 25 normal subjects there was good agreement between the two methods of measuring volume with a mean (SD) difference between measurements of 2.0 (6.6) ml. In 20 patients with previous infarction it was less good with a mean (SD) difference of 4.5 (18.1) ml. The mean (SD) difference of ejection fraction measurements was -0.019 (0.038) in the normal subjects and -0.059 (0.106) in the patients, and the discrepancy between the two techniques was greatest in the patients with a pronounced abnormality of wall motion and low ejection fraction. In a further 25 normal subjects, the agreement between single plane volume measurements in the vertical and horizontal long axis planes was good, indicating that either plane is suitable for rapid measurement. Single plane measurements of left ventricular volume and ejection fraction can be made with the accuracies stated, which are sufficient for routine clinical use except in patients with a pronounced abnormality of wall motion. In combination with measurements of regional wall thickness and motion, previously described, the technique offers a rapid non-invasive assessment of both global and regional left ventricular function.     

Determination of left ventricular volumes and ejection fraction by nuclear magnetic resonance imaging

To determine the ability of nuclear magnetic resonance (NMR) imaging to assess left ventricular (LV) volumes and ejection fraction (EF), we studied 24 patients within 48 hours of single-plane LV angiography. In all patients, a transverse, single-plane NMR acquisition technique was employed with LV end-diastolic (ED) and end-systolic (ES) volumes (V) calculated by a modified area-length algorithm. In nine patients, a multislice acquisition technique was employed with LVEDV and LVESV calculated by a Simpson's rule algorithm. NMR-determined LVV and EF correlated reasonably well with angiographic values (LVEDV: r = 0.75; LVESV: r = 0.90; and LVEF: r = 0.76). The single-plane NMR technique significantly underestimated LVEDV (p less than 0.01), whereas no significant difference was demonstrated for LVESV. As a result, angiographic LVEF was significantly underestimated (p less than 0.05). This underestimation is likely related to off-axis imaging and to the geometric constraints of a single-plane algorithm. In comparing multislice NMR to angiographic data, no significant difference was demonstrated for LVEDV, LVESV, or LVEF. Thus, quantitation of LVV and EF with NMR is feasible, and comparison to angiographic volumes is similar to results reported from other noninvasive imaging modalities. Improvement in current acquisition techniques and software should result in further quantitative potential.     

Contrast-enhanced cardiovascular magnetic resonance imaging of right ventricular infarction.

OBJECTIVES: We assessed the role of late enhancement cardiovascular magnetic resonance imaging (LE-CMR) for the diagnosis of right ventricular infarction (RVI). BACKGROUND: Right ventricular infarction occurs in about one-half of patients with inferior myocardial infarction (MI). It is associated with an unfavorable prognosis, but established methods often lack the diagnostic accuracy to detect it. Late enhancement cardiovascular magnetic resonance imaging accurately detects left ventricular MI. METHODS: Thirty-seven patients with acute inferior MI were included. To test for RVI, they prospectively underwent a physical examination, an electrocardiogram (ECG) for ST-segment elevation in the V4r right precordial lead, and an echocardiogram. After coronary reperfusion, LE-CMR was performed for assessing presence and extent of late enhancement in the right ventricular (RV) wall. The LE-CMR data were compared with the other results; interobserver variability was assessed. The LE-CMR was repeated after 13 months. RESULTS: Late enhancement cardiovascular magnetic resonance imaging detected RVI in 21 of 37 (57%) patients with acute inferior MI. Interobserver variability was very good (kappa 0.83); physical exam was positive for RVI in 7 of 37 (19%) patients, V4r ECG in 13 of 37 (35%) patients, and echocardiogram in 6 of 37 (16%) patients. The LE-CMR findings for RVI showed only mild agreement with findings for RVI on physical exam (kappa 0.30), V(4)r ECG (kappa 0.38), and echocardiography (kappa 0.32). Irreversible injury of the RV persisted at 13 months (kappa 0.85). CONCLUSIONS: In patients with acute inferior MI, RVI is more frequently detected by LE-CMR than by current standard diagnostic techniques. Further CMR studies might allow for analyzing its clinical and prognostic relevance.     

Assessment of right ventricular infarction with contrast-enhanced magnetic resonance imaging

OBJECTIVE: Evaluation of contrast-enhanced magnetic resonance imaging to assess right ventricular infarction in patients with acute inferior myocardial infarction. BACKGROUND: Contrast-enhanced magnetic resonance imaging has been used for assessing scar tissue after left ventricular infarction. The value of contrast-enhanced magnetic resonance imaging to assess right ventricular infarction is unknown and was evaluated. METHODS: Consecutive patients (n=18) with first acute inferior infarction were included. Resting electrocardiogram and right-sided electrocardiogram were acquired to assess right ventricular involvement. Resting cine magnetic resonance imaging was performed to evaluate right ventricular function and volumes, whereas the extent of right ventricular scar tissue was assessed by contrast-enhanced magnetic resonance imaging. Cine magnetic resonance imaging was repeated at 6-months follow-up to re-assess right ventricular function and volumes. RESULTS: Sensitivity and specificity of magnetic resonance imaging were 100 and 78%, respectively, to detect right ventricular infarction (using the right-sided electrocardiogram as the gold standard). At 6 months follow-up, patients with scar tissue on contrast-enhanced magnetic resonance imaging showed right ventricular dilatation. Moreover, the extent of right ventricular scar tissue was linearly related to the severity of right ventricular dilatation. CONCLUSIONS: Contrast-enhanced magnetic resonance imaging permits accurate assessment of right ventricular scar tissue. Patients with extensive right ventricular infarction demonstrate right ventricular dilatation at 6 months follow-up.     

Electrocardiographic predictors of right ventricular volume measured by magnetic resonance imaging late after total repair of tetralogy of Fallot.

BACKGROUND: Right ventricular dysfunction occurs in many patients with significant pulmonary valve regurgitation late after initial total repair of tetralogy of Fallot. Methods to predict which of these patients are at increased risk of late morbidity and mortality are not yet known. HYPOTHESIS: This study evaluated electrocardiographic (ECG) predictors of severe right ventricular dilatation determined by magnetic resonance imaging (MRI) volumes in patients with tetralogy of Fallot late after initial corrective repair. METHODS: We retrospectively reviewed the ECGs and MRI right ventricular volume measurements of 20 patients (age 4.4 to 19.3 years, mean 10.0 years) with significant pulmonary valve regurgitation late after repair of tetralogy of Fallot. All patients had enlarged, hypokinetic right ventricles by echocardiography. The patients were grouped based on an indexed right ventricular end-diastolic volume (RVEDV/BSA) of < 102 ml/m2 (Group 1) or > or = 102 ml/m2 (Group 2). We determined the sensitivity, specificity, positive and negative predictive values of QRS duration, and mean frontal plane QRS axis for predicting right ventricular volumes. RESULTS: A maximal QRS duration of > or = 150 ms or a northwest quadrant frontal plane QRS axis had 85% sensitivity, 86% specificity, 92% positive predictive value, and 75% negative predictive value for predicting an RVEDV/BSA of > or = 102 ml/m2. The mean QRS duration was significantly longer in Group 2 than in Group 1 patients (156 ms vs. 125 ms, p = 0.005). CONCLUSIONS: In patients late after repair of tetralogy of Fallot with significant pulmonary valve regurgitation a maximal manually measured QRS duration of > or = 150 ms and/or a frontal plane QRS northwest quadrant axis can predict patients with marked right ventricular enlargement. The presence of either of these findings on the ECG signifies patients who require further evaluation and consideration for pulmonary valve replacement.     

Findings on magnetic resonance imaging of idiopathic right ventricular outflow tachycardia

We evaluated 20 patients with idiopathic ventricular tachycardia for structural abnormalities using magnetic resonance imaging (MRI) and compared them with 20 controls. Two experienced observers interpreted the MRIs. There were no differences in incidence of qualitative MRI findings in patients compared with controls. These findings do not favor an association between anatomic abnormalities and arrhythmia in these patients.     

磁共振成像在致心律不齐性右室型心肌病的诊断价值

目的回顾性分析27例致心律不齐性右室型心肌病（ARVC）的磁共振成像（MRI）表现,探讨MRI在ARVC的诊断与预后判断中的价值。方法按照1994年WHO关于ARVC的诊断标准,2004年10月至2006年6月共27例临床诊断或病理确诊为ARVC（6例行心脏移植术）,男21例,女6例,平均年龄37．4（15～67）岁。采用1．5T超导MRI扫描仪对心脏形态（脂肪浸润、房室大小）、功能（室壁局部与整体运动功能）、心肌灌注与心肌存活等方面进行综合评价。结果形态学：88．89％（24／27）的病例MRI提示心肌脂肪浸润,62．96％（17／27）右室壁变薄,62．96％（17／27）右室心尖肌小梁明显粗乱,66．67％（18／27）右室流出道扩张,51．85％（14／27）右室心尖扩张,66．67％（18／27）右室下壁及游离壁扩张,40．74％（11／27）合并右房增大。心脏功能：18．52％（5／27）的病例右室局部运动功能异常,70．37％（19／27）整体运动功能异常,右室平均射血分数（EF）35％。40．74％（11／27）的患者合并左室扩大并室壁收缩运动明显减弱。心肌首过灌注示10．52％（2／19）的患者左室受累,36．84％（7／19）的患者左室和右室壁出现异常强化,提示心肌纤维或胶原变性。右室壁强化区域主要位于右室游离壁和右室流出道肌壁,左室则主要位于左室侧壁,少数合并左室心尖或室间隔,5例左室侧壁异常强化经术后病理证实为纤维组织。仅1例表现为右室流出道增宽,但左室心肌显著变薄,收缩运动明显减弱;有3例右室MRI无阳性表现,其中2例左室侧壁室壁变薄并运动异常,延迟显像为异常强化,另1例表现为类似扩张型心肌病样改变。结论MRI高度的软组织对比与多序列成像可对ARVC进行全面诊断与预后评价,但少数以左室异常表现为主而无明显或仅轻微右室异常的病例,MRI易误诊,其左室侧壁段的纤维化为ARVC相对特征表现。右室整体运动异常、广泛纤维脂肪浸润、合并左室扩张并运动异常为其预后不良的指标。     

Quantitation of right ventricular volumes and ejection fraction by three-dimensional echocardiography in patients: comparison with magnetic resonance imaging and radionuclide ventriculography

Three-dimensional echocardiography (3DE) provides volumetric measurements without geometric assumptions. Volume-rendered 3DE has been shown to be accurate for the measurement of right ventricular (RV) volumes in vitro and in animal studies; however, few data are available regarding its accuracy in patients. This study examined the accuracy of 3DE for quantitation of RV volumes and ejection fraction (EF) in patients, compared to magnetic resonance imaging (MRI) and radionuclide ventriculography (RNV). Twenty patients underwent MRI, gated equilibrium RNV, and 3DE using rotational acquisition from both the transesophageal and transthoracic approaches. RV volumes and EF were calculated from the 3DE data using multislice analysis (true Simpson's rule). RV volumes calculated by MRI (end-diastolic volume (EDV) 109.4 +/- 34.3 mls, end-systolic volume (ESV) 59.6 +/- 31.0 mls, and EF 47.7 +/- 17.1%) agreed closely with 3DE. For transesophageal echocardiography, EDV was 108.1 +/- 29.7 mls (r = 0.86, mean difference 1.3 +/- 17.8 mls); ESV was 62.5 +/- 23.8 mls (r = 0.85, mean difference 2.8 +/- 15.1 mls); and EF was 43.2 +/- 11.7% (r = 0.84, mean difference 4.5 +/- 9.7%). For transthoracic echocardiography, EDV was 107.7 +/- 27.5 mls (r = 0.85, mean difference 1.6 +/- 18.2 mls); ESV was 59.7 +/- 22.1 mls (r = 0.93, mean difference 3.2 +/- 19.6 mls); and EF was 45.2 +/- 11.5% (r = 0.86, mean difference 2.0 +/- 9.4%). There were close correlations, small mean differences and narrow limits of agreement between RNV-derived EF (43.4 +/- 12.1%) and both transesophageal (r = 0.95 mean difference 0.2 +/- 3.7%) and transthoracic 3DE (r = 0.95, mean difference 1.8 +/- 5.4%). Three-dimensional echocardiography is a promising new method of calculating RV volumes and EF, comparing well with MRI and RNV. The accuracy of transthoracic 3DE was comparable to that of the transesophageal approach. Three-dimensional echocardiography has the potential to be useful in the clinical assessment of RV disorders.     

新型磁共振对典型及早期致心律失常性右室心肌病诊断价值的探讨

目的 用有黑血技术的新型磁共振（MRI）对典型致心律失常性右室心肌病（ARVC）进行检查，以确定新型MRI诊断ARVC的特异性和敏感性，并通过对确诊的ARVC患的一级亲属行MRI检查，以探讨MRI对早期ARVC的诊断价值。方法 10例ARVC患（除1例猝死首诊外）及其7个家系的54名成员全部接受询问病史，体检，心电图，心脏超声等检查；10例临床患均接受MRI检查，分析和确定其影响特征及诊断条件，在此基础上对部分家系成员行MRI检查以发现早期ARVC患。结果 临床患有阵发性室性心动过速（8／8），晕厥（9／10），心力衰竭（3／10）和猝死（3／10）。心电图均有左束支传导阻滞型阵发性室性心动过速，心室晚电位（VLP）均阳性（8／8）。MRI检查显示临床患均有明显右心室（RV）扩大及室壁广泛强信号，经压脂处理后心肌信号呈岛状或连续中断，为特征性纤维脂肪替代影像，患均有RV运动减低或室壁瘤形成，部分伴左心室受累（3／8）。家系筛选发现8例异常，拟诊为早期ARVC，2例有心电图异常，2例VLP阳性。MRI显示，8例心室壁均有局限性纤维脂肪病的影像改变，4例有RV扩大，2例可疑扩大，6例RV心尖部血流淤滞现象。结论 带黑血技术的新型MRI是目前诊断ARVC和早期ARVC的最具特异性和敏感性的检查手段。     

Quantification of fatty tissue mass by magnetic resonance imaging in arrhythmogenic right ventricular dysplasia

INTRODUCTION: Arrhythmogenic right ventricular dysplasia (ARVD) is a heart muscle disorder in which the pathological substrate is a fatty or fibro-fatty replacement of the right ventricular (RV) myocardium. METHODS AND RESULTS: Magnetic resonance imaging (MRI) studies were performed in 10 patients with arrhythmogenic right ventricular dysplasia and in 24 matched controls in order to assess right ventricular epicardial/intramyocardial fatty tissue mass, RV myocardial mass, and RV functional parameters. Functional abnormalities were found in all ARVD cases. Patients with ARVD showed increased fatty tissue compared to controls (8.2 +/- 4 g vs. 2.0 +/- 1.0 g; P = 0.001), whereas no significant differences were found in RV myocardial mass (29.5 +/- 9.2 g vs. 23.2 +/- 6.7 g; P = NS). A correlation coefficient between 0.87 and 0.97 was found for repeated measurements. CONCLUSION: Quantification of fatty tissue with MRI is feasible and constitutes an objective method for differentiating normal from pathological conditions. This approach may lead to a complete diagnostic assessment of ARVD with the potential application for monitoring the evolution of the disease.