无症状左心功能不全高血压患者的心室晚电位

观察无症状左心功能不全高血压患者心室晚电位（ＶＬＰ），与左心功能的相关性。方法用彩色多普勒及ＫＧＣ－４００检测仪测定５０例高血压患者心室晚电位。结果ＶＬＰ阳性２８例（占５６％），心脏射血分数（ＥＦ）４５±８．７，Ａ／Ｅ１．２１±０．２２。ＶＬＰ的Ｖ４０与ＥＦ、Ａ／Ｅ的相关系数ｒ＝－０．８２，Ｐ＜０．０５。５０例高血压左室肥厚（ＬＶＨ）检出１７例（占３４％），其中２８例ＶＬＰ阳性者１４例（占５０％），２２例ＶＬＰ阴性者３例（占１３．６％）。结论ＶＬＰ与高血压左心功能不全关系密切。     

Early pacing-induced systolic dyssynchrony is a strong predictor of left ventricular adverse remodeling: Analysis from the Pacing to Avoid Cardiac Enlargement (PACE) trial

Background

Right ventricular apical (RVA) pacing is associated with adverse left ventricular (LV) remodeling and biventricular (BiV) pacing may prevent it although the mechanisms remain unclear. The current study aimed to assess the role of early pacing-induced systolic dyssynchrony (DYS) to predict adverse LV remodeling.

Methods

Patients with standard pacing indications and normal LV ejection fraction were randomized either to BiV (n = 89) or RVA pacing (n = 88). Pacing-induced DYS, defined as the standard deviation of the time to peak systolic velocity (Dyssynchrony Index) > 33 ms in a 12-segmental model of LV, was measured by tissue Doppler echocardiography at 1 month.

Results

At 1 month, 59 patients (33%) had DYS which was more prevalent in RVA than BiV pacing group (52% vs. 15%, χ² = 28.3, p < 0.001), though Dyssynchrony Index was similar at baseline (30 ± 14 vs. 26 ± 11 ms, p = 0.06). At 12 months, those developing DYS had significantly lower LV ejection fraction (55.1 ± 9.7 vs. 62.2 ± 7.9%, p < 0.001) and larger LV end-systolic volume (35.3 ± 14.3 vs. 27.0 ± 10.4 ml, p < 0.001) when compared to those without DYS. Reduction of ejection fraction ≥ 5% occurred in 67% (39 out of 58) of patients with DYS, but only in 18% (21 out of 115) in those without DYS (χ² = 40.8, p < 0.001). Both DYS at 1 month (odds ratio [OR]: 4.725, p = 0.001) and RVA pacing (OR: 3.427, p = 0.009) were independent predictors for reduction of ejection fraction at 12 months.

Conclusion

Early pacing-induced DYS is a significant predictor of LV adverse remodeling and the observed benefit of BiV pacing may be related to the prevention of DYS.

Clinical trial registration

Centre for Clinical Trials number, CUHK_CCT00037 (URL: http://www.cct.cuhk.edu.hk/Registry/publictrialrecord.aspx?trialid=CUHK_CCT00037).     

Mechanical dyssynchrony in congestive heart failure: diagnostic and therapeutic implications

Myocardial imaging has been successfully applied to the evaluation of patients with heart failure, particularly identifying candidates who are likely to respond to cardiac resynchronization therapy (CRT). Recent studies have shown the benefits of CRT in heart failure patients with depressed ejection fraction (EF) and a narrow QRS complex, albeit in a small number of patients, and without a placebo arm. In addition, few reports have noted the presence of pathophysiologically relevant mechanical dyssynchrony in patients with heart failure and normal EF. Collectively, these data support the need for a better understanding of cardiac function/dysfunction and its treatment in these patient groups.     

Comparison of ECG Variables of Dispersion of Ventricular Repolarization with Direct Myocardial Repolarization Measurements in the Human Heart

Validation of ECG Variables of Dispersion. Introduction: QT dispersion (QTD) from the 12-tead ECG has been widely adopted as a noninvasive index of dispersion of ventricular repolarization (DVR). QTD, however, has never been validated by direct comparison with myocardial DVR in the human heart. Methods and Results: Monophasic action potential (MAP) recordings obtained in an earlier study were retrospectively matched with 12-lead ECGs available from within 24 hours of the invasive procedure. MAPs were available from an average of 8 ± 3 left endocardial sites in 4 patients with left ventricular hypertrophy (LVH) and 7 patients with normal ECGs, and 6 ± 2 epicardial sites in 3 patients of each group during normal ventricular activation. Local repolarization time (RT) was determined as MAP duration at 90% repolarization plus the local activation time. Dispersion of RT was calculated as the difference between the earliest and latest RT. ECGs were digitized and analyzed with recently described interactive QTD analysis software. In addition to standard QTD (defined as QT_max– QT_min), all currently proposed ECG dispersion variables were compared and correlated with the invasive measurements of DVR. QTD exhibited a reasonable correlation with dispersion of RT (R = 0.67; P < 0.01). Several other variables designed to measure DVR exhibited a similar, but not better, correlation. Among them, the QT peak/QT end ratio in V₃ (R =?0.72; P < 0.01) and averaged over all analyzableleads (R =?0.59; P < 0.01) exhibited a good correlation with dispersion of RT, which was further improved when endocardial measurements were considered alone. T area measures did not correlate with dispersion of RT, but discriminated LVH. Conclusion: DVR can he assessed by means of a 12-lead surface ECG. Several of the variables under study exhibit a similar accuracy in determination of true myocardial dispersion of repolarization. Variables involving the terminal part of repolarization, such as the QT peak/QT ratio, even from a single lead, may add to the determination of DVR from the human heart.     

Echocardiography in heart failure: applications, utility, and new horizons

Echocardiography is well qualified to meet the growing need for noninvasive imaging in the expanding heart failure (HF) population. The recently-released American College of Cardiology/American Heart Association guidelines for the diagnosis and management of HF labeled echocardiography "the single most useful diagnostic test in the evaluation of patients with HF...," because of its ability to accurately and noninvasively provide measures of ventricular function and assess causes of structural heart disease. It can also detect and define the hemodynamic and morphologic changes in HF over time and might be equivalent to invasive measures in guiding therapy. In this article we will discuss: 1) the clinical uses of echocardiography in HF and their prognostic value; 2) the use of echocardiography to guide treatment in HF patients; and 3) promising future techniques for echocardiographic-based imaging in HF. In addition, we will highlight some of the limitations of echocardiography.     

A theoretical and experimental model of ventricular interdependence

Summary Because of the close anatomical association between the ventricles, the volume of one ventricle can directly affect the volume and pressure within the other ventricle. To study the mechanical coupling between the ventricles, we modeled the right and left ventricles as a two-compartment model with right wall (C_iw), septal (C_s), and left wall (C_lw) compliances. Based on the balances of forces across the septum, four equations were obtained to predict the transfer of pressure (P) and volume (V) information from one ventricle to another. The validity of the theoretical analysis was tested first in a physical model and then in a post-mortem heart preparation. The standard errors of estimate comparing the predicted to measured values were low for both the physical model and the post-mortem heart data. All values were significantly related (P<0.05) with r>0.89. The results show excellent correlation between predicted and measured values. This model provides a better understanding of ventricular interdependence and may help to predict effects of hypertrophy and/or myocardial ischemia on ventricular interdependence.This study was supported in part by PHS NIH Grant Nos. HL31644 and HL22843. Dr. Santamore is a recipient of an NIH Research Carrer Development Award No. H101026     

Cross-sectional multiplane transesophageal echocardiographic measurements: comparison with standard transthoracic values obtained in the same setting

BACKGROUND: Several algorithms developed for cost-effective use of transesophageal echocardiography (TEE) propose elimination of "screening" transthoracic echocardiographic (TTE) studies. Cross-sectional measurements obtained by TTE (left atrial diameter [LAD], left ventricular internal dimensions in diastole and systole [LVIDd, LVIDs], septal and posterior wall thickness in diastole [VSTd, PWTd], LV end-diastolic and end-systolic volumes [LVEDV and LVESV], and LV ejection fraction [LVEF]) have not been standardized for TEE. METHODS: Forty-six patients (age 27 to 85 years, 60 +/- 13 years, 25 [54%] women) underwent TEE and TTE studies. TTE was performed while the TEE probe was in place and the patient was still sedated. Standard TTE measurements were compared with corresponding TEE values obtained from mid-esophageal and transgastric views. RESULTS: Standard TTE measurements compared favorably with those obtained by TEE at the mid-esophageal three-chamber view for LAD (3.9 +/- 0.6 cm vs 4.0 +/- 0.7 cm, P = NS) and at the transgastric long-axis view for LVIDd (4.6 +/- 0.8 cm vs 4.7 +/- 0.8 cm, P = NS), LVIDs (3.1 +/- 0.9 cm vs 3.1 +/- 0.9 cm, P = NS), and VSTd (0.95 +/- 0.18 cm vs 0.98 +/- 0.19 cm, P = NS). Biplane TTE and TEE measurements of LVEDV (106 +/- 35 ml vs 112 +/- 38 ml, P = NS), LVESV (37 +/- 23 ml vs 37 +/- 25 ml, P = NS), and LVEF (67 +/- 14% vs 69 +/- 14%, P = NS) also correlated closely. The negative predictive values of TEE measurements for excluding abnormal LAD, LVIDd, VSTd, PWTd, and LVEF as defined by TTE were 83%, 94%, 95%, 97%, and 97%, respectively. CONCLUSION: Cross-sectional TEE measurements as obtained in this study are equivalent to standard TTE dimensions and provide reliable information that may facilitate interpretation of TEE studies in the absence of TTE information.     

Reproducibility of left ventricular measurements with acoustic quantification: the influence of training

Acoustic quantification (AQ) of two-dimensional (2-D) echocardiograms provides online estimation of left ventricular (LV) size and function. However, edge detection with AQ is influenced by gain settings and is therefore operator dependent. Our purpose was to compare AQ and conventional 2-D echo measurements of LV size and function obtained by different operators and to evaluate the influence of training on these measurements. A cardiac sonographer without previous experience with the AQ system was trained by an experienced operator. Twenty-two normal males (age, 28 +/- 4 years) participated in the study. Images were recorded with conventional 2-D and AQ echo from the short-axis and apical four-chamber views. During the initial training period, five subjects were imaged by the sonographer under the supervision of the trainer. At the initial study session, 12 subjects were imaged independently by the two operators. Following a second training period with five different subjects, the same initial 12 subjects were again imaged at a second study session. LV cavity areas were traced from the conventional 2-D echocardiograms and measured from the AQ waveforms at end-diastole and end-systole. Volumes were calculated using the single-plane area-length method. Ejection fraction (EF) was calculated from volumes. Reproducibility was determined by comparing the variability of AQ and conventional 2-D echo measurements obtained at the two sessions. A second training session reduced the operator variability only of the short-axis end-diastolic area measurement (17 +/- 11% vs 6 +/- 5%, P < 0.025). We conclude that a single training session may be adequate for the reproducible estimation of ventricular volumes with the AQ method.