Background
Uncontrolled pulmonary hypertension may cause worse outcomes after transcatheter aortic valve replacement (TAVR), while hemodynamic monitoring is desirable for risk control. Pulmonary artery pressure (PAP) readings obtained by intracardiac Doppler echocardiography were evaluated.
Methods
In 114 patients with symptomatic aortic stenosis and median Society of Thoracic Surgeons scores of 10.5% (interquartile range, 7.7%–15.0%), transfemoral and transapical TAVR was guided by intracardiac Doppler echocardiography. The continuous-wave Doppler beam interrogated the jet of tricuspid regurgitation from the “home view” position. Systolic PAP (PAP s ) was estimated as the sum of the pressure gradient derived from the maximum transtricuspid regurgitation jet velocity and the central venous pressure. Mean PAP (PAP m ) was calculated by the mean gradient method (1) and the Chemla formula (2). Measurements were obtained immediately before and after TAVR.
Results
Pre- and postinterventional readings showed marginal pressure underestimation in comparison with measurements derived from right-heart catheterization: PAP s , −2.7 (95% CI, −3.3 to 2.1) and −1.4 (95% CI, −1.9 to −0.9); PAP m by the mean gradient method, −1.9 (95% CI, −2.2 to −1.6) and −0.1 (95% CI, −0.4 to 0.2). Agreement (95% limits) for PAP s was −8.6 to 3.2 and −6.8 to 4.0; agreement for PAP m by the mean gradient method was −5.4 to 1.6 and −3.4 to 3.2. The repeatability coefficient (95% limits of agreement) for PAP s was excellent: 3.4 (−4.2 to 2.5) and 5.5 (−5.3 to 5.8); repeatability for PAP m was higher by the mean gradient method than by the Chemla method. In ≥85% of patients with pulmonary hypertension, PAP m improved after valve deployment.
Conclusions
Intracardiac Doppler echocardiography–derived monitoring of PAP by the mean gradient method is accurate and well applicable to high-risk TAVR candidates for intraprocedural risk control.
Transcatheter aortic valve replacement (TAVR) offers predictable outcomes and has been established as a valuable alternative to open heart surgery in high-risk and inoperable patients with symptomatic aortic stenosis (AS). Many patients with end-stage AS who are candidates for TAVR have pulmonary hypertension (PH) resulting from “backward transmission” of increased left ventricular filling pressure and secondary pulmonary vasculature abnormalities. PH has been shown to be an independent predictor of mortality after valve replacement and is not only associated with a poor long-term prognosis but can also be a critical factor during TAVR, particularly in very high risk patients. It may regress when congestion improves after TAVR. Particularly in very high risk individuals, intraprocedural monitoring of pulmonary artery pressure (PAP) therefore plays a role, because it helps avoid intrainterventional deterioration and identify those individuals whose PH immediately regresses. Doppler echocardiography is commonly used to estimate PAP, while right-heart catheterization (RHC) represents the gold standard for providing accurate measurements. Provided that the sound conditions are sufficient and the Doppler beam is well aligned with the tricuspid regurgitant jet, reproducibility and reliability of transthoracic echocardiography (TTE) for calculating systolic PAP (PAP s ) and mean PAP (PAP m ) have been repeatedly demonstrated.
In certain respects, intracardiac echocardiography was found to be advantageous for intraprocedural guidance of TAVR. Intracardiac Doppler measurements have not been validated, however. We hypothesized (1) that intracardiac Doppler echocardiography (ICDE) permits PAP monitoring in high-risk patients during TAVR and (2) that ICDE-based calculations of PAP s and PAP m yield satisfactory agreement with invasive measurements and have high repeatability.
Methods
Population
A total of 114 consecutive patients with symptomatic AS underwent transfemoral, transapical, or transaortal TAVR at the Medical University Innsbruck, as recommended. In all individuals, 23-, 26-, or 29-mm Edwards SAPIEN XT or Edwards SAPIEN 3 transcatheter heart valves (Edwards Lifesciences, Irvine, CA) were implanted under general anesthesia or under local anesthesia plus intravenous sedation, also known as monitored anesthesia care. Subjects underwent simultaneous invasive and ICDE-based determination of PAP s and PAP m . Data collection was prospective, and the investigation was approved by the Institutional Review Board of the Medical University Innsbruck. All patients gave informed consent. The prospective study complied with the Declaration of Helsinki.
ICDE-Based Calculations of PAP
An 8-F AcuNav catheter (Siemens Healthcare, Erlangen, Germany) was advanced through the inferior vena cava. The “home view” displaying the tricuspid valve and the right ventricle from the middle of the right atrium was the standard approach. From that position, color Doppler depicts tricuspid regurgitant flow. The continuous-wave Doppler beam can be easily aligned with the regurgitant flow by slightly tilting the tip of the catheter ( Figure 1 ). Maximum and mean systolic right ventricular–to–right atrial pressure gradients were determined using the modified Bernoulli equation (4 × [peak tricuspid regurgitant velocity] 2 ) by tracing the maximum tricuspid regurgitant time-velocity integral ( Figure 2 ). Readings before and after TAVR were obtained while ventilation was stopped and a hemodynamic steady state achieved. All measurements were performed twice by two observers blinded to each other’s findings, and all results were averaged.
Pressures were determined as follows:(1) PAP s : sum of maximum right ventricular–to–right atrial gradient and invasively measured mean central venous pressure (CVP m ) ;(2) PAP m : mean gradient method (i.e., the sum of the mean right ventricular–to–right atrial gradient and invasively measured CVP m ); and (3) PAP m : Chemla formula (0.616 × PAP s + 2 mm Hg).
An echocardiographic examiner meeting the level III criteria of the American Society of Echocardiography manipulated the ICDE catheter and operated the ultrasonographic unit through a sterile drape. Because the echocardiographer was also experienced in invasive techniques, he or she also assisted with the intervention.
Invasive Measurements
A senior anesthesiologist inserted a Swan-Ganz catheter through a standard transjugular approach. Pressure measurements were done at end-expiration and monitored throughout the TAVR procedure. A third observer who was unaware of the echocardiographic results always obtained pre- and postinterventional recordings of PAP under steady-state conditions and simultaneously with the intracardiac Doppler echocardiographic readings.
Statistical Analysis
Depending on the distribution of the continuous data, results are presented as mean ± SD or as medians and interquartile ranges. PAP measurements performed as described above were compared with the conventional catheter-based method (gold standard) to assess the level of agreement. This was accomplished with Bland-Altman plots showing the difference between the measurement methods against their average for each patient, thus quantifying the variation in between-method differences for individual patients and thereby indicating the amount of agreement between methods. The mean difference across the average values is an indicator for a possible bias. In addition, the variation of the mean was used to calculate the 95% limits of agreement (1.96 × SD of the differences). This is the range within which most differences will lie and serves as a reference interval.
Because the ICDE-based measurements were considered possibly liable to interobserver variation, the repeatability of the measurements obtained by both observers was also assessed as suggested by Bland and Altman. The agreement between two measurement methods is compared with the agreement each method has with itself (here only for the ICDE-based measurements), relevant because the repeatability limits the amount of agreement that is possible. To this end, repeatability coefficients were calculated, indicating the expected range of 95% of the differences between the two observers. If the corresponding 95% limits of agreement are similar to the range defined by the plus-or-minus repeatability coefficient, the extent of the lack of agreement between the methods is explained by the amount of lack of repeatability. All data were processed using SPSS version 19 (SPSS, Chicago, IL) and MedCalc version 13 (MedCalc Software, Mariakerke, Belgium).
Results
Study Population and Procedural Outcome
Baseline characteristics of the study population are summarized in Table 1 . Overall, the patients represented a very high risk population, both with respect to their expected natural courses and in terms of their risk with standard surgical valve replacement. Most individuals presented with PH due to chronic obstructive pulmonary disease, congestion, or both. Valve implantation was completed in all patients. There were no intraprocedural deaths. Thirty-day mortality was 7% ( n = 8): one patient (patient 92) experienced left main coronary occlusion, was taken for conversion to open heart surgery, and died on the second postoperative day. This complication was indirectly diagnosed when ICDE displayed akinesia of the anterior wall. Two other patients (patients 56 and 68) died of myocardial infarctions on days 2 and 15, respectively. Another patient (patient 95) developed pericardial hemorrhage due to myocardial wire perforation, directly visualized by ICDE, and died on day 1. Two deaths were due to pneumonia and subsequent septic shock followed by hemodynamic decompensation (patients 15 and 28, both on day 7). One death was caused by terminal renal failure (patient 43, on day 21), and one was due to multiple-organ failure (patient 14, on day 17). Paravalvular leaks were found in 44 patients (39%): no grade III leaks, one grade II leak (1% of all patients), and 43 grade I leaks (38% of all patients).
| Variable | Value |
|---|---|
| Age (y) | 83 (80–85) |
| Body mass index (kg/m 2 ) | 25.2 (4.2%) |
| Women | 62 (54%) |
| EuroSCORE II (%) | 3.66 (2.65–4.99) |
| STS risk score (%) | 10.6 (7.7–15.6) |
| AP mean (mm Hg) | 68 (62–75) |
| Ejection fraction (%) | 49 ± 14 |
| PAP s , median (SD) (mm Hg) ∗ | 48 (13) |
| PAP m , median (SD) (mm Hg) ∗ | 32 (8) |
| PH | 93 (82%) |
| S/P pulmonary embolism | 3 (3%) |
| COPD | 36 (32%) |
| Smokers | 6 (5%) |
| Diabetes mellitus, | 21 (18%) |
| Medications | |
| ACE inhibitors | 39 (34%) |
| Diuretics | 83 (73%) |
| β-blockers | 52 (46%) |
| Digitalis | 7 (6%) |
| Calcium antagonists | 16 (14%) |
| Nitrates | 11 (10%) |
| AT II receptor antagonists | 16 (14%) |
| Balloon valvuloplasty | 13 (11%) |
| S/P PTCA | 24 (21%) |
| Coronary artery disease | 55 (48%) |
| Peripheral artery disease | 29 (25%) |
| S/P heart surgery | 24 (21%) |
| Arterial hypertension | 92 (81%) |
| TAVR access | |
| Transaortal | 16 (14%) |
| Transapical | 37 (32%) |
| Transfemoral | 61 (54%) |
| Aortic valve area (mm 2 ) | 0.55 ± 0.16 |
| PG mean (mm Hg) | 45 (39–60) |
| Other valve disease | |
| Mitral regurgitation | |
| No | 6 (5%) |
| Grade I | 77 (68%) |
| Grade II | 31 (27%) |
| Tricuspid regurgitation | |
| No | 0 (0%) |
| Grade I | 92 (81%) |
| Grade II | 22 (19%) |
ICDE-Based Determination of PAP
Recordable levels of tricuspid regurgitation and measurable jet velocities were found in all patients. ICDE generally revealed a small bias toward lower pre- and postinterventional PAP s values compared with conventional catheter-based measurements ( Figure 3 ). In detail, postinterventional results had an even smaller bias and slightly better agreement compared with preinterventional data. Both Bland-Altman plots ( Figure 3 ) show that the scatter ranges taper toward the right, which is indicative of higher accuracy in the upper measuring ranges.
ICDE-based determination of PAP m was in good agreement with invasive measurements ( Figures 4 and 5 ). Comparing both methods of preinterventional PAP m determination, data from the mean gradient method showed a slightly larger bias toward lower values than data derived with the Chemla formula, but the 95% limits of agreement had a smaller range, which is indicative of better agreement of data derived using the mean gradient method ( Figure 4 ). For post-TAVR data, the bias of both methods was marginal, while the 95% limits of agreement showed similar patterns compared with the preinterventional ones ( Figure 5 ).
The repeatability of the ICDE-based measurements obtained by both examiners is presented in Table 2 . The repeatability coefficients of all three ICDE approaches before TAVR were smaller than those afterward, but all were <6.0 mm Hg. Consequently, the interobserver variability for all examined methods can be considered low. Also, all coefficients conformed with the corresponding limits of agreement, with even the least similar PAP s measurement before TAVR having 95% of the differences between −3.4 and + 3.4 mm Hg, compared with the 95% limits of agreement of −4.2 to 2.5 mm Hg. Hence, with good repeatability and no indication of other factors involved, the agreement evaluation of the ICDE-methods seems sound.
| Examiners A and B | Repeatability coefficient (mm Hg) | 95% limits of agreement (mm Hg) |
|---|---|---|
| PAP s before TAVR | 3.4 | −4.2 to 2.5 |
| PAP s after TAVR | 5.5 | −5.3 to 5.8 |
| PAP m (MGM) before TAVR | 3.8 | −3.4 to 4.1 |
| PAP m (MGM) after TAVR | 4.5 | −4.5 to 4.5 |
| PAP m (Chemla formula) before TAVR | 2.1 | −2.5 to 1.6 |
| PAP m (Chemla formula) after TAVR | 3.9 | −3.8 to 4.0 |
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