Left bundle branch block and echocardiography in the era of CRT.

Left ventricular (LV) dyssynchrony is a key pathophysiology in the era of cardiac resynchronization therapy (CRT). Left bundle branch block (LBBB) is the main substrate for CRT, and understanding the electrical pathophysiology is important in assessing the effects of CRT. Three-dimensional voltage mapping systems clearly demonstrate the typical propagation pattern characterized as propagation from the mid or apical septum to the lateral or posterior wall through the apex, which appears as a U shape. The electrical characteristics in LBBB closely associate with mechanical dyssynchrony, which is visualized as a septal flash motion. This rapid motion can be detected well by M-mode, tissue Doppler, and speckle tracking imaging. However, intraventricular discoordination between the septum and free wall is also a key to the response to CRT. We classified M-mode septum images into 10 patterns and septal strain pattern into two patterns. Through detailed analysis, we found that septal contraction contributes to intraventricular coordination. Therefore, in addition to septal flash, subsequent analysis of wall motion patterns also provides additional information about myocardial contractibility and the severity of electrical dyssynchrony. Recently, 3-dimensional speckle tracking imaging was introduced and used as a novel method to image electromechanical coupling. Because activation imaging by 3-dimensional speckle tracking can visualize similar U-shaped propagation images to those by 3-dimensional voltage mapping systems, it is hoped that this method will contribute to further research. Until now, it has not been fully understood how electrical dyssynchrony is expressed as mechanical abnormalities; therefore, continuous study will be required in the future.

Prognostic significance of persistent restrictive filling pattern after cardiac resynchronization therapy.

BACKGROUND: Cardiac resynchronization therapy (CRT) may improve left ventricular (LV) diastolic dysfunction as well as systolic dysfunction. Diastolic dysfunction is a key for prognosis in patients with heart failure; therefore, we aimed to clarify the impact of CRT on diastolic function and prognosis. METHODS: In 67 patients who underwent CRT, LV diastolic function was assessed by pulsed Doppler transmitral flow pattern at baseline and 1 week after CRT, and classified into restrictive filling pattern (RFP) and non-RFP groups. Volume responders were defined by reduction of LV end-systolic volume >15% at 6 months after CRT. The clinical endpoint comprised death from any cause or unplanned hospitalization for a major cardiovascular event (MACE). RESULTS: During the follow-up period (479 ± 252 days), 26 patients (38.8%) had reached the endpoint of MACE. In Cox proportional hazard analyses, RFP at 1 week after CRT was associated with the endpoints independently of age and New York Heart Association (NYHA) class IV at baseline. Thirty (44.8%) patients were identified as volume responders, who had better prognosis than non-responders. Patients were classified into 4 groups based on their filling pattern at 1 week after CRT and volume responses. The worst prognosis was observed in the RFP and non-responder group, and the best was observed in the non-RFP and responder group. For the remaining 2 groups with intermediate prognosis, the RFP and responder group showed poorer prognosis compared to the non-RFP and non-responder group. CONCLUSIONS: Persistent RFP after CRT may be a strong prognostic predictor, which should be treated with more intensive therapy to improve the prognosis of patients following CRT.

Variability in amplitude and stimulation threshold values in motor evoked potential (MEP) monitoring during the resection of brain lesions.

OBJECTIVE: Criteria for motor evoked potential (MEP) monitoring include the amplitude criterion and threshold criterion. The aim of our study for the amplitude criterion during removal of brain lesions was to determine a suitable stimulus intensity that can reduce the variability in amplitudes. We also assessed the usefulness of the threshold criterion and amplitude criterion by comparing the variability between the two methods as a preliminary study. METHODS: Seventeen patients including 12 cases with no neurological deterioration after surgery were enrolled in this study. The amplitudes in various stimulus intensities and the stimulation threshold (ST) were repeatedly measured during surgery. The stimulus intensities used in the amplitude criterion are described as 'the ST just after dura opening (ST(0))+additional intensity'. The variability was assessed with the coefficient of variation (CV). RESULTS: With direct cortical stimulation (DCS), the CVs of amplitudes were significantly lower at stimulus intensities of more than ST(0)+4 mA, with the smallest at ST(0)+10 mA. The CV of STs was significantly smaller than that of amplitudes. CONCLUSIONS: The variability in the amplitude criterion was significantly reduced using stimulus intensities of more than ST(0)+4 mA. The variability in the threshold criterion was significantly smaller than that of the amplitude criterion, even when using a strong stimulus intensity. SIGNIFICANCE: The maximal stimulus intensity with no body motion should be used in the amplitude criterion for intraoperative MEP elicited by DCS.

Novel dyssynchrony evaluation by M-mode imaging in left bundle branch block and the application to predict responses for cardiac resynchronization therapy.

BACKGROUND: To determine an appropriate M-mode method in assessing left ventricular (LV) dyssynchrony in left bundle branch block (LBBB), and to assess feasibility of the method to predict cardiac resynchronization therapy (CRT) responses. METHODS AND RESULTS: Fifty-one patients with LBBB were enrolled. Among them 31 patients underwent CRT. In addition to original septal to posterior wall motion delay (SPWMD), first peak-SPWMD was proposed as time of difference between the first septal displacement and the maximum displacement of the posterior. If an early septal point was not present, anatomical M-mode was used to visualize an early septal displacement spreading scan-area until inferoseptal wall. CRT responders were defined as LV end-systolic volume reduction (>15%) at 6 months after CRT. Twenty patients (65%) were identified as CRT responders. First peak-SPWMD in responders was significantly higher than those in nonresponders, although SPWMD did not differ between groups. Strong predicting ability of first peak-SPWMD was revealed (first peak-SPWMD: 80/90/83%; SPWMD: 35/100/58%), and area under the curve in receiver operating characteristic analysis of first peak-SPWMD (0.88) was significantly higher than that of SPWMD (0.61) (p<0.05). CONCLUSION: In patients with LBBB, time differences between early septal and delayed displacement of posterolateral wall on M-mode images were the appropriate dyssynchrony parameter, and could improve the predictive ability for CRT responses.

Tissue Doppler imaging dyssynchrony parameter derived from the myocardial active wall motion improves prediction of responders for cardiac resynchronization therapy.

BACKGROUND: The aim of this study was to propose modified tissue Doppler imaging (TDI) parameters derived from the first active wall motion and to assess them for the better prediction of cardiac resynchronization therapy (CRT) responders in comparison with to original TDI parameters. METHODS AND RESULTS: In 61 patients with CRT, time from QRS onset to peak velocities by TDI (Ts), which were derived from active wall motion identified by longitudinal strain rate (LSR) value, were assessed. Time from QRS onset to the negative peak of LSR (TLSR) was also assessed. Modified standard deviation of Ts in 12 left ventricular (LV) segments (Ts-SD), that of TLSR (TLSR-SD), differences of Ts between septum and lateral wall (Ts-SL), and that of TLSR (TLSR-SL) were calculated. Original Ts-SD and Ts-SL were calculated by previously described methods. Responders were defined as patients with LV end-systolic volume reduction (>15%) at 6 months after CRT: 35 patients (57%) were identified as CRT responders. Area under the receiver-operating characteristics curve (AUC) of modified Ts-SD (0.87) was significantly higher than that of Ts-SD (0.65), Ts-SL (0.62), and TLSR-SL (0.69). AUC of modified Ts-SL was significantly higher than those of Ts-SD, and Ts-SL. AUC of TLSR-SD (0.82) also was significantly higher than that of Ts-SD. CONCLUSIONS: Modified TDI dyssynchrony parameters derived from the first active wall motion improve the ability to predict responders to CRT.

End-systolic and end-diastolic left atrial volume assessment by two-dimensional echocardiography: a comparison study with magnetic resonance imaging.

BACKGROUND: The left atrial volume (LAV) is an important indicator of the severity of certain diseases, and measuring LAV through the cardiac cycle may enable the evaluation of various left atrium (LA) functional parameters. The results of two-dimensional (2D) echocardiographic LAV measurement methods vary, and no technique is accepted as being optimal. OBJECTIVE: This study compared the accuracy of end-systolic and end-diastolic LAV measurements by 2D echocardiography with those obtained by magnetic resonance imaging (MRI). METHODS: Fifty consecutive patients who underwent both echocardiography and MRI due to clinical reasons with nonselective cardiac disease were studied. LAVs by 2D echocardiography were obtained with the prolate ellipsoid (PE), biplane area-length (AL), and modified Simpson's (MS) methods. RESULTS: End-systolic and end-diastolic LAVs calculated by each method correlated significantly with MRI results (P < 0.0001). The prolate ellipsoid method provided LAVs that most correlated with MRI results, and the biplane area-length and modified Simpson's methods provided LAVs with small mean differences (<5 ml) compared to MRI results. CONCLUSION: All three methods of 2D echocardiographic LAV measurement provide valuable LAV data, suggesting the possibility of evaluating various LA functional parameters.

Mechanical dyssynchrony assessed by speckle tracking imaging as a reliable predictor of acute and chronic response to cardiac resynchronization therapy.

Speckle tracking echocardiography (STE) has the potential to detect the heterogeneous initiation of active myocardial contraction, which is the primary cause of left ventricular (LV) systolic dysfunction in patients with mechanical dyssynchrony. This study was designed to assess the ability to predict response to cardiac resynchronization therapy (CRT) of STE-derived dyssynchrony parameters in comparison with invasive hemodynamic assessments. Thirty patients referred for CRT were studied. The time difference of first peak (Td-(first peak)) and the maximum peak (Td-(max peak)) on the radial strain-time curves of the earliest and the latest segments were measured as the dyssynchrony parameter. Peak positive dP/dt (dP/dt(max)) was measured as the indicator of global LV systolic performance. CRT responders were defined as patients with LV end-systolic volume reduction greater than 15% at 3 months after CRT. CRT increased the dP/dt(max) compared with the baseline study (P < .001). Percent changes in the dP/dt(max) (dP/dt(max)) were significantly correlated with Td-(first peak) (R = 0.743, P < .001), but weakly correlated with Td-(max peak) (R = 0.390, P = .03). Twenty patients (66%) were identified as chronic CRT responders. Receiver operating characteristics analysis revealed that Td-(first peak) shared a similar ability with dP/dt(max) to detect chronic responders (Td-(first peak) >167.0 ms, area under the curve [AUC] 0.945; dP/dt(max) >16.2%, AUC 0.934) compared with Td-(max peak) (>194.5 ms, AUC 0.820). STE-derived Td-(first peak) showed a reliable ability to predict the acute and chronic response to CRT as well as dP/dt(max).

Analysis of the origin of cardiac wall motion that constitutes myocardial velocity-time curves in patients with left bundle branch block.

Septal and lateral wall myocardial velocity-time curves from tissue Doppler imaging were analyzed to determine wall motion from which the velocity originated in 34 patients with left bundle branch and systolic dysfunction (ejection fraction < 45%). Longitudinal strain rate by speckle tracking imaging was assessed to identify whether corresponding wall motion was active or passive. All lateral peak velocities during the ejection period were derived from delayed active movement. However, septal peak velocities were more numerous and complex. Septal peak velocities during pre-ejection were derived from the first active movement in 29 patients (85.2%). Septal peak velocities during the ejection period were derived from the second active movement in 20 patients, passive movement in 9 patients, and first active movement in 5 patients. Because septal peak velocities were consistent with various wall motion types, identification of the origin of septal peak velocities, including during pre-ejection, may be important in identifying LV dyssynchrony based on the propagation of first active myocardial movements.