Abstract
Background
Changes in the dicrotic notch characteristics in the aortic pressure waveform have not been adequately studied with mitral transcatheter edge-to-edge repair (M-TEER). In this study, we sought to determine the changes in the dicrotic notch index (DNI) with M-TEER and identify their significance in determining procedural success.
Methods
We retrospectively analyzed patients undergoing M-TEER between 2019 and 2022 at our institution. DNI ([systolic-dicrotic pressure]/[systolic-diastolic pressure]) was calculated from invasive ascending aortic pressure waveforms. The cut point for change in DNI was determined and used to compare differences in composite clinical outcomes of mortality and heart failure hospitalization. To identify the determinants of change in DNI, variables including post-M-TEER MR and change in forward stroke volume (FSV) were measured.
Results
Of the 145 patients included in the study cohort, DNI significantly increased after M-TEER (0.49 ± 0.11 to 0.52 ± 0.11, p < 0.001). A cut point of 2.71% change in DNI identified higher probability of event-free survival at 1 year. Using this cut point, change in DNI was an independent predictor of event-free survival (hazard ratio: 0.45 [95% CI: 0.21-0.99], p = 0.01). Of the studied variables, change in FSV was the only predictor of change in DNI (hazard ratio: 0.187 [95% CI: 0.072-0.302], p = 0.002) with significant correlation (r = 0.30, p < 0.001).
Conclusions
DNI increases after M-TEER, and the magnitude of increase in DNI is associated with better clinical outcomes. Further, increase in FSV correlates with increase in DNI. DNI measured during M-TEER procedure provides an additional simple measure of procedural success.
Highlights
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There is a need for a simple measure of the success of mitral transcatheter edge-to-edge repair.
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Changes in dicrotic notch index correlate positively with forward stroke volume.
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Dicrotic notch index is a predictor of clinical outcomes at 1 year after mitral transcatheter edge-to-edge repair.
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Dicrotic notch index provides a practical approach to assessing procedural success.
Introduction
In recent years, mitral transcatheter edge-to-edge repair (M-TEER) has become an important treatment option for high-surgical-risk patients with primary mitral regurgitation (MR) and symptomatic patients with secondary MR despite guideline-directed medical therapy. The success of the M-TEER procedure is traditionally defined by a reduction in MR without generating significant mitral stenosis. , To date, the change in forward stroke volume (FSV) has not been used as an indicator of the success of M-TEER. Although it is reasonable to assume that FSV would increase with the correction of MR, this has not been shown conclusively in large part due to the infrequent usage of right heart catheterization during M-TEER.
Most patients undergoing M-TEER have arterial pressure monitoring as the procedure is performed under general anesthesia. Many centers, including ours, use aortic pressure monitoring with a pigtail catheter in the aortic root, which provides a landmark for transseptal puncture as well as the monitoring of left ventricular (LV) pressure when needed. However, more granular investigations of the pressure tracing itself have not been conducted. For instance, the changes in the dicrotic notch in the aortic pressure waveform have not been adequately investigated during valvular interventions. We have previously reported the importance of the dicrotic notch index (DNI) during the transcatheter aortic valve replacement procedure, especially to understand residual aortic regurgitation. However, the changes in DNI during M-TEER have not been previously studied.
In this study, we sought to determine whether patient outcomes after the M-TEER procedure are predicted by changes in DNI and if the changes in DNI correlate with changes in FSV.
Materials and Methods
Patient Population
This retrospective study identified patients who underwent M-TEER between 2019 and 2022 at our institution. High-risk surgical patients with primary MR and secondary MR patients with persistent symptoms despite guideline-directed medical therapy were considered candidates for M-TEER. Patients with interpretable aortic invasive hemodynamic waveforms during M-TEER were included in the study. Baseline clinical variables and follow-up information were obtained from electronic medical records. This study was approved by the Cleveland Clinic Institutional Review Board.
Measurements
Invasive aortic pressure waveforms were retrieved from SyngoDynamics software (Siemens Medical Solutions Inc). The measurements of systolic, diastolic, and dicrotic notch pressures were obtained from aortic waveforms. DNI was calculated from systolic, diastolic, and pulse pressure as: <SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='(systolicpressure−dicroticnotchpressure)/(systolicpressure−diastolicpressure)’>(systolicpressure−dicroticnotchpressure)/(systolicpressure−diastolicpressure)(systolicpressure−dicroticnotchpressure)/(systolicpressure−diastolicpressure)
( systolic pressure − dicrotic notch pressure ) / ( systolic pressure − diastolic pressure )
. Mean left atrial (LA) pressure was obtained from invasive LA pressure waveforms during M-TEER. Transthoracic echocardiography was used to measure FSV before and after the procedure. FSV was calculated using left ventricular outflow track (LVOT) velocity time integral multiplied by LVOT area. LVOT area was calculated from LVOT diameter, which was measured in the parasternal long-axis view. The systolic ejection period (SEP) was measured from the time of aortic valve opening to its closure. Changes in DNI and FSV were defined as <SPAN role=presentation tabIndex=0 id=MathJax-Element-2-Frame class=MathJax style="POSITION: relative" data-mathml='[(postprocedure−preprocedure)/(preprocedure)]∗100′>[(postprocedure−preprocedure)/(preprocedure)]∗100[(postprocedure−preprocedure)/(preprocedure)]∗100
[ ( postprocedure − preprocedure ) / ( preprocedure ) ] ∗ 100
. Other echocardiographic variables were obtained from echocardiographic reports before and after M-TEER. The median time to pre-M-TEER transthoracic echo was 46.4 days (25th-75th percentile range: 14-85 days). The post-M-TEER median time to a complete transthoracic echo was 35.6 days (25th-75th percentile range: 0.5-50.6 days).
Patient Outcomes
The primary clinical outcome was the composite of all-cause mortality and heart failure hospitalization. These data were obtained from electronic medical chart review.
Statistical Analysis
All continuous variables were described as mean ± SD. All discrete variables were described as n (%). Two-tailed paired t-test was used to determine the significance of change in continuous variables. Two-tailed unpaired t-test was used to compare differences between primary MR (PMR) and secondary (SMR) MR. Chi-squared test was performed to compare discrete variables. Multivariate linear regression was performed to identify predictors of change in DNI using change in FSV, LA pressure, and MR severity as independent variables. Correlation between FSV and DNI was tested using Pearson’s test. The optimal cutoff for categorizing patients into higher and lower DNI change post-M-TEER was identified using the “surv_cutpoint” function in the survminer R package. Kaplan-Meier estimates, generated to compare event-free survival between the two DNI groups, utilized the log-rank test and the survminer package in R. The optimal cut point identification was done using the maximally selected rank statistics from R software version 4.3.2 (R Core Team, Vienna, Austria). This cut point was used to compare differences in clinical outcomes. Data analysis was performed using SPSS software version 27 (IBM, Chicago, Illinois).
Results
Patient Population
Of the 382 patients who underwent M-TEER between 2019 and 2022, 145 were included in the final analysis, while 237 were excluded due to unavailable or suboptimal aortic waveforms ( Figure 1 ). Of the 145 included patients, 91 (63%) had PMR and 54 (37%) had SMR. The median age of the study population was 79 (interquartile range, 71 to 85 years), and 37% of the patients were female. The mean Society of Thoracic Surgeons risk score was 6.52 ± 6.26. Patients with PMR were significantly older than those with SMR (81 vs. 72 years, p < 0.001). SMR patients had a significantly higher body mass index (29.33 ± 6.7 vs. 25.84 ± 4.8, p = 0.001). A significantly higher percentage of SMR patients had hypertension compared to PMR patients (94 vs. 79%, p = 0.01). As expected, the ejection fraction was significantly lower in SMR patients compared to PMR patients (40.37% ± 14.16% vs. 57.69% ± 9.46%, p < 0.001), and the LV diastolic and systolic internal diameters were significantly higher in SMR patients ( Table 1 ).
| Overall (N = 145, 100%) | Primary MR (N = 91, 63%) | Secondary MR (N = 54, 37%) | p -Value | |
|---|---|---|---|---|
| Clinical variables | ||||
| Age, y, median (IQR) | 79 (71-85) | 81 (75-86) | 72 (65-80) | <0.001 |
| Female, % | 54 (37) | 36 (40) | 18 (33) | 0.45 |
| BMI | 27.14 ± 5.8 | 25.84 ± 4.8 | 29.33 ± 6.7 | 0.001 |
| STS risk score | 6.52 ± 6.26 | 5.92 ± 6.45 | 7.61 ± 5.81 | 0.14 |
| Hypertension | 123 (85) | 72 (79) | 51 (94) | 0.01 |
| Diabetes mellitus | 34 (23) | 19 (21) | 15 (28) | 0.34 |
| Coronary artery disease | 103 (71) | 63 (69) | 40 (74) | 0.53 |
| ESRD | 3 (2) | 0 | 3 (6) | 0.05 |
| Atrial fibrillation | 102 (70) | 62 (68) | 40 (74) | 0.45 |
| Echocardiographic variables | ||||
| EF, % | 51.07 ± 14.22 | 57.69 ± 9.46 | 40.37 ± 14.16 | <0.001 |
| LV internal diameter diastole, cm | 5.42 ± 0.85 | 5.09 ± 0.73 | 5.91 ± 0.78 | <0.001 |
| LV internal diameter systole, cm | 4.02 ± 1.15 | 3.46 ± 0.74 | 4.84 ± 1.15 | <0.001 |
| FSV, ml | 61.01 ± 21.16 | 59.94 ± 20.43 | 62.86 ± 22.47 | 0.44 |
| MR severity, % | ||||
| Mild | 3 (2) | 1 (1) | 2 (4) | 0.27 |
| Moderate | 20 (14) | 10 (11) | 10 (18) | |
| Severe | 119 (82) | 77 (88) | 42 (78) | |
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