Transcatheter Aortic Valve Implantation Improves Cardiac Sympathetic Nerve Activity on 123I-Metaiodobenzylguanidine Myocardial Scintigraphy in Severe Aortic Valve Stenosis

Left-atrial volume reduction reflects improvement of cardiac sympathetic nervous function in patients with severe aortic stenosis after transcatheter aortic valve replacement

Trans-catheter aortic valve replacement (TAVR) is an excellent alternative intervention for surgical aortic valve replacement. Cardiac sympathetic nervous (CSN) function and left atrial (LA) volume are both important prognostic factors in patients with aortic stenosis (AS) after TAVR. The relationship between the two clinical factors is unknown, however. This retrospective observational study aimed to assess the correlation between CSN function and LA volume in 48 symptomatic patients with severe AS (median age: 85 years, IQR 82-88 years; 81% female) before and after TAVR. CSN function was assessed by performing ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy before and 6 months after TAVR, and the delayed heart-to-mediastinum ratio (dHMR) and washout rate (WR) were calculated. We also performed transthoracic echocardiography near the same time. TAVR improved the dHMR, WR, and LA volume index (LAVI) (dHMR: median 2.89 [IQR 2.62-3.23] vs. 2.98 [2.49-3.25], p = 0.0182; WR: 28% [24-38] vs. 23% [16-32], p < 0.0001; LAVI: 47.7 mL/m² [37.8-56.3] vs. 41.2 mL/m² [33.7-56.1], p = 0.0024). In multiple linear regression analysis, the percentage change in LAVI from baseline to post-TAVR (∆LAVI%) was an independent predictor of change in dHMR from baseline to post-TAVR (β =  - 0.35, p = 0.0110). In conclusion, LA volume reduction reflected CSN functional improvement after TAVR. In patients with TAVR, ∆LAVI% might be a valuable parameter for evaluating CSN functional recovery.

Serial changes in cardiac sympathetic nervous function after transcatheter aortic valve replacement: A prospective observational study using 123I-meta-iodobenzylguanidine imaging

BACKGROUND

Transcatheter aortic valve replacement (TAVR) can rapidly improve cardiac sympathetic nervous function (CSNF) within 2 weeks in patients with aortic stenosis (AS). However, whether such short-term improvements will be sustained thereafter remains unclear.

METHODS

Patients with severe AS who underwent TAVR between October 2017 and June 2019 were enrolled in this single-center, prospective, observational study. 123I-meta-iodobenzylguanidine imaging was performed at baseline, within 2 weeks after TAVR, and at 6 to 12 months post-TAVR to evaluate the heart-mediastinum ratio (H/M) and washout rate.

RESULTS

Of 183 consecutive patients, 75 (19 men; median age: 86 years) were evaluated. The late H/M significantly improved within 2 weeks after TAVR (P = .041) and further improved over 6 to 12 months after TAVR (P = .041). Multivariate analysis revealed that the baseline mean aortic valve pressure gradient (mPG) was an independent predictor of mid-term improvement in the late H/M (> 0.1) (P = .037). Patients with a high baseline mPG (≥ 58 mmHg) exhibited a significantly greater increase in the late H/M than those with a low baseline mPG (< 42 mmHg) (0.24 vs 0.01; P = .029).

CONCLUSION

CSNF demonstrated sustained improvement from within 2 weeks after TAVR until 6 to 12 months later. Such improvement was related to baseline hemodynamic AS severity.

Cardiac sympathetic dysfunction in left ventricular hypertrophy caused by arterial hypertension and degenerative aortic stenosis

BACKGROUND

To evaluate cardiac sympathetic innervation in hypertensive patients with left ventricular (LV) hypertrophy (H) and aortic stenosis (AS) submitted to transcatheter aortic valve implantation (TAVI).

METHODS AND RESULTS

Twenty-two hypertensive elders (82 ± 5 years) with severe AS and significant LVH (> 122 g·m-2 in women and > 149 g·m-2 in men) were compared with 14 patients with uncomplicated essential hypertension (HT) with similar degree of LVH and 10 controls. 123I-metaiodobenzylguanidine (MIBG) and 99mTc-tetrofosmin SPECT acquisitions were obtained to assess sympathetic innervation and LV perfusion. The innervation/perfusion mismatch score was taken as an indicator of cardiac sympathetic dysfunction. The imaging protocol was repeated 6 months after TAVI. Regional MIBG uptake was more heterogeneous in HT and AS patients than controls, and therefore, innervation/perfusion mismatch score was higher in both AS (9 ± 8) and HT (5 ± 2) than controls (1 ± 1, P < .001). On multivariate analysis, significant LVH was the major predictor of impaired LV sympathetic innervation (OR 19.45, 95% CI 1.87-201.92; P = .013). After TAVI, no differences in measures of LV sympathetic innervation were evident, although only a marginal LV mass reduction was observed (- 5.4 ± 2.4 g).

CONCLUSIONS

Cardiac sympathetic innervation is impaired in patients with LVH, either with AS or not, and is not impacted significantly by TAVI procedure.

Clinical Implications of Changes in Respiratory Instability Following Transcatheter Aortic Valve Replacement

BACKGROUND

Respiratory instability, which can be quantified using respiratory stability time (RST), is associated with the severity and prognostic impact of the disease in patients with chronic heart failure. However, its clinical implications in patients with severe aortic stenosis receiving transcatheter aortic valve replacement (TAVR) remain unknown.

METHODS

Patients who received TAVR and had paired measurements of RST at a baseline and one week following TAVR were prospectively included. Changes in RST following TAVR and its impact on post-TAVR heart failure readmissions were investigated.

RESULTS

Seventy-one patients (median age, 86 years old; 35% men) were included. The baseline RST was correlated with the severity of heart failure including elevated levels of plasma B-type natriuretic peptide (p < 0.05 for all). RST improved significantly following TAVR from 34 (26, 37) s to 36 (33, 38) s (p < 0.001). Post-TAVR lower RST (<33 s, n = 18) was associated with a higher 2-year cumulative incidence of heart failure readmission (21% vs. 8%, p = 0.039) with a hazard ratio of 5.47 (95% confidence interval 0.90-33.2).

CONCLUSION

Overall, respiratory instability improved following TAVR. Persistent respiratory instability following TAVR was associated with heart failure recurrence.

Factors Influencing Cardiac Sympathetic Nervous Function in Patients With Severe Aortic Stenosis: Assessment by 123I-Metaiodobenzylguanidine Myocardial Scintigraphy

BACKGROUND

Numerous studies have shown that 123I-metaiodobenzylguanidine (MIBG) scintigraphy, an index of cardiac sympathetic nervous (CSN) activity, is useful for predicting prognosis in patients with heart failure. However, the factors influencing the CSN activity of patients with severe aortic stenosis (AS) remain unclear.

METHODS

We enrolled 91 patients with severe AS who underwent 123I-MIBG scintigraphy, coronary computed tomography (CCT), and transthoracic echocardiography. When CCT angiography (CCTA) showed an obstructive epicardial artery, invasive coronary angiography was performed within 1 week of CCTA.

RESULTS

There were 21 male and 70 female patients with a mean age of 84±5 years. Eighty-five (85) patients (93%) had hypertension and 13 patients (14%) had diabetes. Two (2) patients (2%) had previous myocardial infarction and eight (9%) had a previous coronary intervention. All patients had severe AS: aortic valve area was 0.63±0.18 cm² and the mean pressure gradient was 56±19 mmHg. Regarding 123I-MIBG parameters, early heart-to-mediastinum (H/M) ratio was 3.1±0.5, delayed H/M ratio was 2.8±0.6, and the washout rate (WR) was 35%±13%. Multivariable linear regression analysis showed that coronary artery disease (β=-0.30, p=0.002) was an independent predictor of delayed H/M ratio, and that aortic valve area (β=-0.20, p=0.048) was an independent predictor of WR.

CONCLUSIONS

Our findings suggest that coronary artery disease is an independent predictor of delayed H/M ratio, and aortic valve area is an independent predictor of WR in patients with severe AS.

Prognostic value of cardiac 123 I-metaiodobenzylguanidine imaging for predicting cardiac events after transcatheter aortic valve replacement

Aims

In patients with aortic valve stenosis (AS), cardiac sympathetic nervous (CSN) dysfunction and its improvement after transcatheter aortic valve replacement (TAVR) have been reported. The prognostic impact of CSN function remains unclear. This study investigated the prognostic value of cardiac ¹²³I‐metaiodobenzylguanidine (MIBG) imaging for predicting cardiac events after TAVR.

Methods and results

This single‐centre prospective observational study enrolled patients with AS between July 2017 and May 2019. MIBG scintigraphy was performed before and soon after TAVR to evaluate the late heart–mediastinum ratio (L‐H/M). Patients were classified into three pairs of groups based on the baseline and post‐TAVR L‐H/M (≥2.0 or <2.0) and on the presence of TAVR‐related improvement in L‐H/M. The study endpoint was the occurrence of major adverse cardiac events (MACE), defined as a composite of all‐cause death, non‐fatal myocardial infarction, and hospitalization due to heart failure. Among the 187 consecutive patients who underwent TAVR, 107 (27 men; median age: 86 years) were evaluated. Over a median follow‐up of 366 days, 15 (14.0%) patients had MACE. The incidence of MACE was significantly low in patients with L‐H/M improvement and/or high post‐TAVR L‐H/M (≥2.0). Baseline L‐H/M and frailty were associated with poor response of L‐H/M to TAVR treatment. TAVR‐related improvement in L‐H/M had significant effects on MACE, with an adjusted hazard ratio of 0.233 (95% confidence interval, 0.064–0.856; P = 0.028).

Conclusions

TAVR‐related improvement in L‐H/M was an independent predictor of cardiac events, 1 year after TAVR. Cardiac MIBG imaging is useful for predicting cardiac events after TAVR.

Impact of Prosthesis-Patient Mismatch After Transcatheter Aortic Valve Replacement on Changes in Cardiac Sympathetic Nervous Function

The impact of prosthesis-patient mismatch (PPM) after transcatheter aortic valve replacement (TAVR) on changes in cardiac sympathetic nervous (CSN) function remains unclear. Using 123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy, we investigated the impact of PPM after TAVR on CSN activity.We enrolled 44 of 117 patients with severe aortic stenosis who underwent TAVR for analysis in the present study. We conducted 123I-MIBG scintigraphy at baseline and at about 9 months after TAVR. Differences between baseline and post-TAVR 123I-MIBG parameters were compared between cases with and without PPM.There were 17 and 27 patients with and without PPM, respectively. Those without PPM exhibited significantly decreased left ventricular mass index (122 ± 36 g/m² versus 108 ± 30 g/m², P < 0.001) following TAVR, whereas those with PPM did not (117 ± 21 g/m² versus 110 ± 17 g/m², P = 0.09). Significant improvements in delayed heart-to-mediastinum (H/M) ratio (2.8 ± 0.4 versus 3.0 ± 0.4, P = 0.004) and washout rate (WR) (33% ± 10% versus 24% ± 12%, P < 0.001) were observed after TAVR in patients without PPM but not in those with PPM. Multivariable linear regression analysis revealed PPM to be a negative predictor of improvements in delayed H/M ratio and WR.Delayed H/M ratio and WR improve significantly after TAVR in the absence of PPM, whereas these improvements are not observed in patients with PPM. Hence, the presence of PPM is a negative predictor of improvements in delayed H/M ratio and WR in patients undergoing TAVR.

SPECT vs. PET in cardiac innervation imaging: clash of the titans

PURPOSE

We aim to provide an overview of the conventional single photon emission computed tomography (SPECT) and emerging positron emission tomography (PET) catecholamine analogue tracers for assessing myocardial nerve integrity, in particular focusing on 18F-labeled tracers.

RESULTS

Increasingly, the cardiac sympathetic nervous system (SNS) is being studied by non-invasive molecular imaging approaches. Forming the backbone of myocardial SNS imaging, the norepinephrine (NE) transporter at the sympathetic nerve terminal plays a crucial role for visualizing denervated myocardium: in particular, the single-photon-emitting NE analogue 123I-meta-Iodobenzylguanidine (123I-mIBG) has demonstrated favorable results in the identification of patients at a high risk for cardiac death. However, cardiac neuronal PET agents offer several advantages including improved spatio-temporal resolution and intrinsic quantifiability. Compared to their 11C-labeled counterparts with a short half-life (20.4 min), novel 18F-labeled PET imaging agents to assess myocardial nerve integrity have the potential to revolutionize the field of SNS molecular imaging. The longer half-life of 18F (109.8 min) allows for more flexibility in the study design and delivery from central cyclotron facilities to smaller hospitals may lead to further cost reduction. A great deal of progress has been made by the first in-human studies of such 18F-labeled SNS imaging agents. Moreover, dedicated animal platforms open avenues for further insights into the handling of radiolabeled catecholamine analogues at the sympathetic nerve terminal.

CONCLUSIONS

18F-labeled imaging agents demonstrate key properties for mapping cardiac sympathetic nerve integrity and might outperform current SPECT-based or 11C-labeled tracers in the long run.