Estimation of left ventricular end-diastolic pressure by color M-mode Doppler echocardiography and tissue Doppler imaging.

OBJECTIVES: The aim of this study was to estimate left ventricular end-diastolic pressure (LVEDP) noninvasively by tissue Doppler imaging and color M-mode echocardiography. MATERIAL AND METHODS: We studied 3 groups of patients who were proven by angiography to be free of significant coronary artery lesions (<40% stenosis) with an LVEDP < 10 mm Hg (group A: n = 24; 16 men, 18 women; mean age +/- SD = 55 +/- 13 years), an LVEDP of 10 to 15 mm Hg (group B: n = 21; 17 men, 4 women; mean age 56 +/- 11 years), or an LVEDP > 15 mm Hg (group C: n = 35; 20 men, 15 women; mean age 58 +/- 9 years). Tissue Doppler imaging of the lateral mitral annulus and color M-mode imaging of the mitral valve in the apical 4-chamber view were obtained with an echocardiographic system. Early and late diastolic velocities (Em and Am, respectively), Em deceleration time (EmDT), Am time (Am-t), and mitral propagation velocity time delay (VpDT) were measured in each patient. RESULTS: In group A, sensitivity and specificity for EmDT < or = 100 ms, Am-t < or = 90 ms, Em/Am > or = 1, and VpDT < or = 45 ms were found to be 0.57 and 0.89, 0.66 and 0.88, 0.86 and 0.92, and 0.73 and 0.89, respectively. In group B, sensitivity and specificity for EmDT 100 to 120 ms, Am-t 90 to 110 ms, Em/Am 1 to 0.5, and VpDT 45 to 60 ms were found to be 0.57 and 0.84, 0.69 and 0.82, 0.66 and 0.75, and 0.55 and 0.83, respectively. In group C, sensitivity and specificity for EmDT > 120 ms, Am-t > 110 ms, Em/Am < 0.5, and VpDT > 60 ms were found to be 0.88 and 0.81, 0.71 and 0.80, 0.86 and 0.72, and 0.78 and 0.86, respectively. CONCLUSION: The EmDT, Am-t, Em/Am, and VpDT measurements obtained noninvasively by left ventricular tissue Doppler imaging and mitral flow propagation velocity were found to be useful in the estimation of LVEDP.     

Effect of pericardium on left ventricular early filling assessed by pulsed Doppler echocardiography

Pericardial effect on left ventricular early filling was studied in six dogs by use of pulsed Doppler echocardiography. Rapid dextran infusion was used to manipulate left atrial pressure. Left ventricular peak early filling velocities before and after pericardiectomy were measured at different levels of left atrial pressure with right atrial and left ventricular pressures. Peak early filling velocity correlated with mean left atrial pressure before and after pericardiectomy. Before pericardiectomy, when mean right atrial pressure exceeded 12 mm Hg, further increase of the velocity was not observed in spite of volume loading. After pericardiectomy, peak early filling velocity became higher and the slope of the relation line between mean left atrial pressure and the velocity became steeper than before pericardiectomy. When the filling pressure was denoted by the transmural mean left atrial pressure, the points on the relation line before pericardiectomy fell along the relation line after pericardiectomy. We conclude the pericardium exerts an external constraint on left ventricular early filling. Therefore we should not consider the absolute but the transmural filling pressure when estimating left ventricular early diastolic function with use of Doppler-derived left ventricular early filling velocity.     

Evaluation of left ventricular filling pressure by transthoracic Doppler echocardiography in the intensive care unit

OBJECTIVE: To determine whether Doppler transmitral and pulmonary venous flow pattern is related to left ventricular filling pressures in critically ill patients. DESIGN: Prospective clinical investigation. SETTING: Medical intensive care unit of a university hospital. PATIENTS: Fifty-four mechanically ventilated patients (age, 63 +/- 16 yrs) were investigated via transthoracic echocardiography and Doppler. Main diagnoses were pneumonia (31%), acute exacerbation of chronic obstructive pulmonary disease (24%), congestive heart failure (11%), and poisoning (11%). INTERVENTIONS: Doppler examinations were performed simultaneously with measurements of pulmonary artery occlusion pressure via a right heart catheter. MEASUREMENTS AND MAIN RESULTS: Pulmonary artery occlusion pressure correlated with transmitral peak E-wave velocity (r =.46) and E/A ratio (r =.55). Pulmonary artery occlusion pressure inversely correlated with deceleration time of the transmitral E-wave (r = -.52), pulmonary venous peak S-wave velocity (r = -.37), and systolic fraction of the pulmonary forward flow (r = -.56). An E/A ratio >2 predicted a pulmonary artery occlusion pressure >18 mm Hg with a positive predictive value of 100%. A duration of pulmonary venous A-wave reversal flow exceeding the duration of the transmitral A-wave forward flow predicted a pulmonary artery occlusion pressure >15 mm Hg with a positive predictive value of 83%. A systolic fraction of the pulmonary venous forward flow <0.4 predicted a pulmonary artery occlusion pressure >12 mm Hg with a positive predictive value of 100%. CONCLUSION: Transmitral and pulmonary venous flow patterns measured by transthoracic Doppler echocardiography can be used to estimate the left ventricular filling pressure in critically ill patients.     

Variability of Doppler echocardiographic indexes of left ventricular filling in transplant recipients and in normal subjects

This study examines the reproducibility and variability of pulsed wave Doppler versus continuous wave Doppler ultrasound indexes of left ventricular filling in cardiac allograft recipients and in normal subjects. The following indexes were studied: isovolumic relaxation time, pressure half-time, peak early mitral flow velocity, and peak mitral flow velocity after atrial systole. Intraobserver and interobserver variability were assessed by regression analysis. Individual components of variance (subject, reader, beat, day, and tracing) were estimated in a subset of five patients and five normal subjects, and estimated total variance defined for each group. Temporal (day-to-day) variability for 95% confidence was estimated for these patients and for normal subjects. Temporal variability in the group from which the subsets were drawn was measured from absolute and percent change in values on two occasions. Estimated and observed 95% confidence limits were compared. Intersubject variability was the largest component of variance in both transplant recipients and in normal subjects. For all indexes in transplant recipients (in the absence of rejection) and normal subjects, observed absolute mean differences (+/- 2 standard deviations) between values from recordings taken on two different days were larger than the 95% confidence limits estimated from the components of variance analysis. The observed 95% limits for transplant recipients versus normal subjects were as follows: isovolumic relaxation time, 20 msec versus 6 msec; pressure half-time, 16 msec versus 9 msec; peak early mitral flow velocity, 32 cm per second versus 17 cm per second; and peak mitral flow velocity after atrial systole, 28 cm per second versus 10 cm per second.(ABSTRACT TRUNCATED AT 250 WORDS)     

Age-dependency of left ventricular filling dynamics and relaxation as assessed by pulsed Doppler echocardiography

Summary. Left ventricular diastolic function was assessed from transmitral flow velocity curves as measured by Doppler echocardiography in healthy individuals aged 21–69 years, each decade comprising 12 subjects. By ageing, progressive changes in the various filling parameters were observed. When comparing the youngest and oldest age groups, the ratio between peak velocities in early and late diastole decreased from 2.0±0.3 to 1.2±0.3 (P<0.001). The filling fraction of first third of diastole decreased from 54 ± 5% to 45 ± 4% (P<0.001). Isovolumic relaxation time increased from 61 ± 11 ms to 77 ± 12 ms (P<0.01). Correlation coefficients of velocity ratio, filling fraction and isovolumic relaxation time vs. age were r= -0.71 (P<0.001), r= -0.56 (P<0.001) and r= 0.44 (P<0.001), respectively. When isovolumic relaxation time and age were used together in multivariate regression analysis, only age was an independent predictor of velocity ratio and filling fraction. Stroke volume, peak velocity in left ventricular outflow tract, heart rate and systolic blood pressure were similar in all age groups. Thus, velocity ratio and filling fraction indicated a relative filling shift towards late diastole by ageing and were more sensitive than s?ystolic parameters in reflecting age-related changes in cardiac function. The changes could be explained neither by delayed relaxation nor by change in systolic parameters. When using Doppler echocardiography for evaluation of left ventricular filling, agematching of reference groups is necessary.     

Complementary role of two-dimensional and Doppler echocardiography in the diagnosis of left ventricular free-wall rupture.

We describe a case of left ventricular free-wall rupture of the heart in which the use of two-dimensional and Doppler echocardiography provided the diagnosis. The echocardiographic findings in this condition are discussed and a previously unreported finding is described.     

Measurement of left ventricular dp/dt by simultaneous Doppler echocardiography and cardiac catheterization.

Left ventricular dp/dt is a useful isovolumic index for evaluating acute directional changes in myocardial contractility. To test the hypothesis that Doppler echocardiography can measure left ventricular dp/dt by using the mitral regurgitation velocity curve, 14 patients with at least a mild degree of mitral regurgitation (four with coronary artery disease, four with valvular heart disease, four with dilated cardiomyopathy, one with carcinoid, and one with mitral valve prosthesis) were studied by continuous-wave Doppler echocardiography. Simultaneously, left ventricular pressure was measured with a manometer-tipped catheter to generate actual dp/dt. Curves of left ventricular pressure and mitral regurgitant Doppler-derived velocities of three cardiac cycles were digitized at 1-msec intervals. The rate of Doppler-derived velocity increase was converted to a rate of pressure increase by using the modified Bernoulli equation. Mean dp/dt during various time intervals of the mitral regurgitation velocity envelope (1 to 2 m/sec, 2 to 3 m/sec, and 1 to 3 m/sec) corresponding to left ventricular-left atrial pressure differences of 12, 20, and 32 mm Hg, respectively, were calculated. Doppler-derived left ventricular dp/dt (y) correlated with catheter-derived left ventricular dp/dt (x) as follows: at the 1 to 2 m/sec interval, y (mm Hg/sec) = 0.84x + 137, r = 0.91, SEE = 90; at the 2 to 3 m/sec interval, y = 1.1x - 89, r = 0.96, SEE = 80; and at the 1 to 3 m/sec interval, y = 1.1x + 23, r = 0.98, SEE = 50.(ABSTRACT TRUNCATED AT 250 WORDS)     

Restrictive left ventricular filling and preserved ventricular function: a limitation in the noninvasive estimation of pulmonary wedge pressure by Doppler echocardiography.

Pulmonary wedge pressure (PWP) can be estimated from the ratio of transmitral early peak flow velocity to flow propagation velocity measured by Doppler. Discrepancies observed in the application of the method prompted us to design this prospective study, aimed at detecting potential limitations of the method. We studied a total of 32 patients admitted to a cardiac intensive care unit, using a Swan-Ganz catheter. Correlation between invasive- and Doppler-estimated PWP was fairly good (r = 0.58). Analysis of discrepant cases led to the identification of a subgroup of 6 patients in whom PWP was largely underestimated because of unexpectedly high values of flow propagation velocity (71 +/- 15 cm/s vs 37 +/- 10 cm/s in the rest of the group; P =.0001). All of them had in common a restrictive Doppler filling pattern and preserved left ventricular systolic function. Exclusion of this group showed an improvement in the correlation coefficient to r = 0.72. In conclusion, PWP can be estimated by the Doppler early peak flow velocity to flow propagation velocity ratio, although a significant underestimation of PWP may be observed in patients with a restrictive filling pattern and preserved ventricular function.     

New aspects on the assessment of left ventricular dyssynchrony by tissue Doppler echocardiography: comparison of myocardial velocity vs. displacement curves

The purpose of this study is to assess the incremental value of tissue Doppler (TDI) derived displacement curves (TDint) compared to TDI velocity curves (TDvel) for the evaluation of left ventricular (LV) dyssynchrony (LVD). About 25 patients (pts.) with systolic heart failure were studied by TDvel and TDint. Four TDI sample volumes were placed at the basal and four at the mid ventricular myocardium, utilising two imaging planes. LV dyssynchrony (LVD) was defined as an interregional delay of >40 ms corrected for heart rate. 10 pts. had synchronous contraction, 15 pts. LVD as defined by two experts (EC). To determine diagnostic accuracy and intra-observer variability two identical sets of 100 documents (25 pts. × two imaging planes × two modalities) were produced and presented in random order to one trained (TR) and two untrained (UR) readers. The TR more frequently classified documents as unreadable (7.5 vs. 3.5%, P < 0.05) but more often as correct, i.e., consistent with EC (72.0 vs. 57.8%, P < 0.001). 8.7% of the documents were classified as unreadable using TDvel, 1.0% when applying TDint (P < 0.001). The mean value of correct classification of all 3 readers was 54.3% (TDvel only), 70.7% (TDint only), and 77.7% (combining both modalities), (P < 0.001). The kappa value for TR and TDint was 0.68, for TDvel 0.29. For UR, kappa did not differ (TDint: 0.58; TDvel 0.51). TDint is superior to TDvel in accuracy, reproducibility, and applicability for skilled and unskilled investigators when evaluating LVD by TDI. The combined application of TDint and TDvel is optimal.     

Augmentation of atrial contribution to left ventricular filling in IDDM subjects as assessed by Doppler echocardiography

Left ventricular diastolic function was assessed by pulsed Doppler echocardiography in 21 subjects (mean age 48 yr) with insulin-dependent diabetes mellitus (IDDM) and without evidence of ischemic heart disease and in 21 healthy control subjects of similar age and sex distribution. The peak mitral valve flow velocities during the early rapid filling phase (E) and during late atrial filling (A) were measured, and the ratio of these peak flow velocities (E:A) was calculated. E was similar in both groups, but A was higher (P less than .01) in the diabetic group. Thus, E:A was lower (1.19 +/- 0.24 vs. 1.65 +/- 0.67; P less than .01) in the diabetic subjects than in the control subjects. On subgroup analysis, 6 patients with cardiac autonomic neuropathy had lower E:A than the patients with no such disorder (0.99 +/- 0.15 vs. 1.29 +/- 0.25; P less than .05). E:A was not related to the duration of diabetes, presence of retinopathy, HbA1, or blood glucose levels. In conclusion, the atrial contribution to left ventricular filling seems to be augmented in diabetic subjects. This finding indirectly supports the view that left ventricular compliance is already reduced in asymptomatic diabetic subjects.     

Hand-carried echocardiography for assessment of left ventricular filling and ejection fraction in the surgical intensive care unit

Purpose

To better define the reliability of left ventricular ejection fraction (LVEF) and left ventricular filling, as determined by either hand-carried ultrasound (HCU) or formal transthoracic echocardiography (TTE), in the critically ill surgical patient.

Materials and Methods

Prospective cross-sectional study of 80 surgical intensive care unit patients with concomitant (<30 minutes apart) formal TTE and clinician-performed cardiac HCU. Visual estimates of LVEF and left ventricular filling (“underfilled” vs “normally filled”) were recorded, both by clinicians performing HCU and fellowship-trained echocardiographers.

Results

Bland-Altman plot analysis of LVEF estimates revealed good interobserver agreement between HCU and formal TTE (% LVEF mean bias, −2.2; with 95% limits of agreement, ±22.1). This was similar to agreement between independent echocardiography observers (% LVEF mean bias, 1.3; with 95% limits of agreement, ±21.0). However, assessments of left ventricular filling demonstrated only fair to moderate interobserver agreement (κ = 0.22-0.40). Of note, a greater percentage of the 5 standard acoustic windows were obtainable using formal TTE (72% vs 56%).

Conclusions

Formal TTE offers no advantage over HCU for determination of LVEF in critically ill surgical patients, even though the former allows for a more complete examination. However, estimations of left ventricular filling only demonstrate fair to moderate interrater agreement and thus should be interpreted with care when used as markers of volume responsiveness.     

实时三维超声心动图和组织多普勒显像评价左心室收缩同步性的相关性研究

目的：比较实时三维超声心动图和组织多普勒显像在分析正常人和扩张型心肌病患者左心室收缩同步性中的临床价值。方法：60例研究对象分为二组：A组为31例健康志愿者，B组为29例扩张性心肌病患者。均行实时三维经胸超声心动图和组织多普勒检查，得到左室舒张末期容积、收缩末期容积、左室射血分数、心电图Q波起始点距离16节段和12节段容积最小容积点时间间隔的标准差及其最大差（分别为Tmsv16-SD，Tmsv12-SD；Tmsv16-Dif，Tmsv-2Dif）。对组织多普勒显像进行定量评价，得到心电图Q波起始点到等容收缩波峰值、收缩波峰值、舒张早期及晚期波峰值、最大应变的标准差（分别为Tmvc-SD，TS-SD，Te-SD，Ta-SD，TE-SD）。结果：B组的LVEF显著小于A组（P〈0．05）。B组的同步性参数值均大于A组（P〈0．01或P〈0．001）。TIVC-SD，TE-SD与Tmsv-16-SD,Tmsv12-SD，Tmsv16-Dif,Tmsv12-Dif显著相关（r=0．583～0．743，均P〈0．001），Ts-SD，Te-SD与Tmsv16SD和Tmsv16-Dif中等相关（r=0．561～0．605，均P〈0．001），Ts-SD，Te-SD与Tmsv12-SD和Tmsv12-Dif的相关性较弱（r=0．410～0．588，均P〈0．05），Ta-SD与实时三维超声的各参数均不相关（r=0．264～0．383，均P〉0．05）。结论：实时三维超声心动图和组织多普勒均能够评价左室心肌收缩同步性，两种方法的评价结果具有一定的相关性。     

Three-dimensional echocardiography with tissue harmonic imaging shows excellent reproducibility in assessment of left ventricular volumes.

We studied the reproducibility of repeated measurements of left ventricular (LV) volumes by 2-dimensional (biplane method of disks) and 3-dimensional echocardiography (coaxial scanning) with tissue harmonic imaging. Ten healthy subjects underwent estimation of LV volumes by transthoracic echocardiography twice within 1 week by 2 different operators to investigate interexamination and operator variance. In addition, the analysis of LV volume was done manually by 2 observers to assess both interobserver and intraobserver variances. With 3D echocardiography, observer variation had the greatest impact on variance. Operator variability showed important contributions to total variance with the use of 2D echocardiography. The reproducibility of 3D echocardiography and tissue harmonic imaging is excellent and comparable to magnetic resonance imaging techniques; 3D echocardiography therefore should provide a powerful tool for noninvasive LV volume estimation.     

超声心动图评估左心室充盈压的研究进展

心力衰竭是人类死亡的主要原因之一,其中左心室射血分数(LVEF)正常和LVEF减低的患者约各占一半[1-2].左心室充盈压(LVFP)升高是左心收缩功能不全的特征之一[3];LVEF正常的患者中,LVFP升高是左心舒张功能不全的主要指标[4-5].因此,评估LVFP在诊断心功能不全方面具有重要临床意义.LVFP即舒张期中左心室与左心房之间的压力阶差,反映了左心室的前负荷状况,受循环血容量、心肌收缩力和舒张特性等影响.     

超声心动图评估左心室充盈压的研究进展

心力衰竭是人类死亡的主要原因之一,其中左心室射血分数(LVEF)正常和LVEF减低的患者约各占一半[1-2].左心室充盈压(LVFP)升高是左心收缩功能不全的特征之一[3];LVEF正常的患者中,LVFP升高是左心舒张功能不全的主要指标[4-5].因此,评估LVFP在诊断心功能不全方面具有重要临床意义.LVFP即舒张期中左心室与左心房之间的压力阶差,反映了左心室的前负荷状况,受循环血容量、心肌收缩力和舒张特性等影响.     

Noninvasive optimization of left ventricular filling using esophageal Doppler

OBJECTIVE: To confirm whether the descending aortic blood flow velocity waveform variable of flow time corrected for heart rate, measured using an esophageal Doppler transducer, can be used for noninvasive optimization of left ventricular (LV) filling. SETTING: ICU and operating theater. SUBJECTS: Forty-three mechanistically ventilated patients in the ICU or undergoing cardiothoracic surgery in whom a pulmonary arterial catheter was in situ. INTERVENTIONS: LV preload was a) increased from hypovolemic states (pulmonary arterial occlusion pressure [PAOP] less than 8 mm Hg) by fluid challenge, b) decreased from normovolemic states (PAOP 10 to 15 mm Hg) by either iv nitrates or intravascular fluid loss, and c) decreased from heart failure or fluid overload states (PAOP greater than 20 mm Hg) by iv nitrates. No other maneuver was performed concurrently. MEASUREMENTS AND MAIN RESULTS: Descending aortic blood flow was measured by an esophageal Doppler transducer. Corrected flow time was calculated by dividing systolic flow time by the square root of the cycle time. PAOP and corrected flow time increased after fluid challenges in hypovolemic states, and decreased when LV preload was decreased from normovolemic states. However, when preload was decreased from overload states, PAOP always decreased, but the corrected flow time usually increased before any subsequent decrease. The greatest value of corrected flow time corresponded with the maximal stroke volume seen. CONCLUSIONS: Esophageal Doppler measurement of aortic blood flow can be used for rapid, noninvasive optimization of LV filling in mechanically ventilated patients.     

Right ventricular strain in pulmonary embolism by Doppler tissue echocardiography.

For patients with submassive pulmonary embolism, failure of the right ventricle can often be visualized by 2-dimensional echocardiography. We used strain analysis to demonstrate changes in the regional right ventricular free wall performance during the acute and recovery stages of pulmonary embolism.     

Fetal tissue Doppler echocardiography: detection rates of cardiac structures and quantitative assessment of the fetal heart.

OBJECTIVES: Tissue Doppler echocardiography (TDE) has been developed in adult cardiology, but only recently has it been applied to fetal heart studies. We implemented TDE on a high-resolution ultrasound system used for prenatal scanning by changing the Doppler settings, but without specific TDE equipment, to study cardiac tissue motion of normal fetuses in the second and third trimesters. METHODS: Using color Doppler settings optimized for low velocity motion assessment, detection rates of cardiac structures were measured in 47 fetuses. With pulsed Doppler, axial diastolic and systolic cardiac wall velocities were recorded in another 30 fetuses. RESULTS: In all fetuses TDE could detect cardiac wall motion. The right ventricular wall and the level of the atrioventricular valves were most easily seen. Axial contraction velocities of the fetal heart increased with gestational age. CONCLUSIONS: TDE can be used to study normal fetal cardiac function throughout gestation. A regular ultrasound system without additional hardware or software is suitable for screening studies using TDE.     

组织多普勒超声心动图评价冠心病患者心室舒张功能

目的采用组织多普勒技术观察冠心病患者心室舒张功能的改变及左室和右室舒张功能的关系。方法研究24例正常健康人和20例冠心病患者,应用多普勒超声技术测量二尖瓣口及三尖瓣口舒张期血流速度;应用组织多普勒超声技术测量二尖瓣环一左室侧壁交界处及三尖瓣环一右室侧壁交界处心肌运动频谱。测量二尖瓣及三尖瓣舒张早期血流速度（E）、舒张晚期血流速度（A）及E／A,心肌舒张早期运动速度（Em）、晚期运动速度（Am）及Em／Am,测量E／Em。结果与正常组比较,冠心病组左室舒张期二尖瓣血流速度E／A显著减小（P〈0．01）,三尖瓣血流E／A亦显著减小（P〈0．01）;组织多普勒所测左右心室Em、Am、Em／Am均减小（P〈0．01）,E/Em增大（P〈0．01）;冠心病组左室与右室间E/Em比值高度相关（r=0．83）。结论冠心病患者的左室舒张功能异常,伴有右室舒张功能的改变,右室与左室舒张功能的改变相关。应用组织多普勒和频谱多普勒联合评价心室舒张功能,纠正了频谱多普勒评价心室舒张功能出现的假正常现象。     

多普勒组织成像评价左乳腺癌放疗早期左心功能

目的 探讨多普勒组织成像(DTI)技术在评价左乳腺癌放疗早期左心功能方面的应用价值.方法 35例左乳腺癌术后患者按照放疗进程分为放疗前、放疗3周,放疗5周,分别在3个时间点测量二尖瓣环前壁、下壁、前间隔、后壁收缩期峰值速度(Sa),舒张早期峰值速度(Ea),舒张晚期峰值速度(Aa),并计算Ea/Aa比值.结果 放疗5周二尖瓣环前壁的Ea、Ea/Aa分别为(7.85±2.31)cm/s、0.97±0.25,前间隔的Ea、Ea/Aa分别为(7.71±2.70)cm/s、0.99±0.24,放疗前前壁Ea、Ea/Aa分别为(10.87±2.69)cm/s、1.30±0.24,前间隔Ea、Ea/Aa分别为(10.61±2.81)cm/s、1.31±0.23,两个时间点比较差异有统计学意义(t=5.037、5.641、4.401、5.710,P均＜0.01),而Sa、Aa与放疗前比较差异无统计学意义(t=0.843、1.462、0.889、1.180,P均＞0.05);放疗5周二尖瓣环下壁、后壁各指标及放疗3周各指标与放疗前比较差异均无统计学意义(P均＞0.05).结论 DTI可定量分析左侧乳腺癌术后放疗患者早期左心功能.