Role of advanced left ventricular imaging in adults with aortic stenosis

Left ventricular ejection fraction: clinical, pathophysiological, and technical limitations

Risk stratification of cardiovascular death and treatment strategies in patients with heart failure (HF), the optimal timing for valve replacement, and the selection of patients for implantable cardioverter defibrillators are based on an echocardiographic calculation of left ventricular ejection fraction (LVEF) in most guidelines. As a marker of systolic function, LVEF has important limitations being affected by loading conditions and cavity geometry, as well as image quality, thus impacting inter- and intra-observer measurement variability. LVEF is a product of shortening of the three components of myocardial fibres: longitudinal, circumferential, and oblique. It is therefore a marker of global ejection performance based on cavity volume changes, rather than directly reflecting myocardial contractile function, hence may be normal even when myofibril's systolic function is impaired. Sub-endocardial longitudinal fibers are the most sensitive layers to ischemia, so when dysfunctional, the circumferential fibers may compensate for it and maintain the overall LVEF. Likewise, in patients with HF, LVEF is used to stratify subgroups, an approach that has prognostic implications but without a direct relationship. HF is a dynamic disease that may worsen or improve over time according to the underlying pathology. Such dynamicity impacts LVEF and its use to guide treatment. The same applies to changes in LVEF following interventional procedures. In this review, we analyze the clinical, pathophysiological, and technical limitations of LVEF across a wide range of cardiovascular pathologies.

Prognostic Value of Cardiac Magnetic Resonance Feature Tracking Strain in Aortic Stenosis

BACKGROUND

Recent data have suggested that global longitudinal strain (GLS) could be useful for risk stratification of patients with severe aortic stenosis (AS). In this study, we aimed to investigate the prognostic role of GLS in patients with AS and also its incremental value in relation to left ventricular ejection fraction (LVEF) and late gadolinium enhancement (LGE).

METHODS

We analysed all consecutive patients with AS and LGE-CMR in our institution. Survival data were obtained from office of national statistics, a national body where all deaths in England are registered by law. Death certificates were obtained from the general register office.

RESULTS

Some 194 consecutive patients with aortic stenosis were investigated with CMR at baseline and followed up for 7.3 ± 4 years. On multivariate Cox regression analysis, only increasing age remained significant for both all-cause and cardiac mortality, while LGE (any pattern) retained significance for all-cause mortality and had a trend to significance for cardiac mortality. Kaplan-Meier survival analysis demonstrated that patients in the best and middle GLS tertiles had significantly better mortality compared to patients in the worst GLS tertiles. Importantly though, sequential Cox proportional-hazard analysis demonstrated that GLS did not have significant incremental prognostic value for all-cause mortality or cardiac mortality in addition to LVEF and LGE.

CONCLUSIONS

Our study has demonstrated that age and LGE but not GLS are significant poor prognostic indicators in patients with moderate and severe AS.

Echocardiographic Evaluation of Aortic Stenosis: A Comprehensive Review

Echocardiography represents the most important diagnostic tool in the evaluation of aortic stenosis. The echocardiographic assessment of its severity should always be performed through a standardized and stepwise approach in order to achieve a comprehensive evaluation. The latest technical innovations in the field of echocardiography have improved diagnostic accuracy, guaranteeing a better and more detailed evaluation of aortic valve anatomy. An early diagnosis is of utmost importance since it shortens treatment delays and improves patient outcomes. Echocardiography plays a key role also in the evaluation of all the structural changes related to aortic stenosis. Detailed evaluation of subtle and subclinical changes in left ventricle function has a prognostic significance: scientific efforts have been addressed to identify the most accurate global longitudinal strain cut-off value able to predict adverse outcomes. Moreover, in recent years the role of artificial intelligence is increasingly emerging as a promising tool able to assist cardiologists in aortic stenosis screening and diagnosis, especially by reducing the rate of aortic stenosis misdiagnosis.

Interaction between the left ventricular ejection fraction and left ventricular strain and its relationship with coronary stenosis

BACKGROUND

Coronary artery stenosis (CAS) is the most common type of heart disease and the leading cause of death in both men and women globally. CAS occurs when the arteries that supply blood to the heart muscle harden and become narrower due to plaque buildup - cholesterol and other material - on their inner walls. As a result, the heart muscle cannot receive the blood or oxygen it needs. Most heart attacks happen when a blood clot suddenly cuts off the hearts' blood supply, causing permanent heart damage.

AIM

To analyze the relationship between the left ventricular ejection fraction (LVEF), left ventricular strain (LVS), and coronary stenosis.

METHODS

A total of 190 participants were enrolled in this trail. The control group comprised 93 healthy individuals, and observation group comprised 97 patients with coronary heart disease who were hospitalized between July 2020 and September 2021. Coronary lesions were assessed using the Gensini score, and the LVEF and LVS were measured using magnetic resonance imaging (MRI). The interaction between the LVEF and LVS was examined using a linear regression model. The relationship between LVEF and coronary stenosis was examined using Spearman’s correlation.

RESULTS

The LVEF of the observation group was lower than that of the control group. The left ventricular end-systolic volume (LVESV) and left ventricular end-diastolic volume (LVEDV) of the observation group were significantly higher than those of the control group (P < 0.05). The longitudinal and circumferential strains (LS, CS) of the observation group were significantly higher than those of the control group; however, the radial strain (RS) of the observation group was significantly lower than that of the control group (P < 0.05). LVS, LS, and CS were significantly negatively correlated with the LVEF, and RS was positively correlated with the LVEF. There were significant differences in the LVEF, LVESV, and LVEDV of patients with different Gensini scores; the LVEF significantly decreased and the LVESV and LVEDV increased with increasing Gensini scores (P < 0.05). In the observation group, the LVEF was negatively correlated and the LVESV and LVEDV were positively correlated with coronary stenosis (P < 0.05).

CONCLUSION

The LVEF measured using MRI is significantly linearly correlated with LVS and negatively correlated with coronary stenosis.

Prognostic implications of impaired longitudinal left ventricular systolic function assessed by tissue Doppler imaging prior to transcatheter aortic valve implantation for severe aortic stenosis

Change in longitudinal left ventricular (LV) systolic function serves as an early marker of the deleterious effect of aortic stenosis (AS) and other cardiac comorbidities on cardiac function. We explored the prognostic value of tissue Doppler imaging (TDI)-derived longitudinal LV systolic function, defined by the peak systolic average of lateral and septal mitral annular velocities (average S') among symptomatic patients with severe AS undergoing transcatheter aortic valve implantation (TAVI). 297 consecutive patients with severe AS undergoing TAVI at three european centers with available average S' at preprocedural echocardiography were retrospectively included. The primary endpoint was the Kaplan Meier estimate of all-cause mortality. After a median 18 months (IQR 12-18) follow-up, 36 (12.1%) patients had died. Average S' was associated with all-cause mortality (per 1 cm/sec decrease: HR 1.29, 95%CI 1.03-1.60, p = 0.025), the cut-off of 6.5 cm/sec being the most accurate. Patients with average S' < 6.5 cm/sec (55.2%) presented characteristics of more advanced LV remodeling and functional impairment along with higher burden of cardiac comorbidities, and experienced higher all-cause mortality (17.6% vs. 7.5%, p = 0.007), also when adjusted for in-study outcome predictors (adj-HR: 2.69, 95%CI 1.22-5.93, p = 0.014). Results were consistent among patients with preserved ejection fraction, normal-flow AS, high-gradient AS and in those without LV hypertrophy. Longitudinal LV systolic function assessed by average S' is independently associated with long-term all-cause mortality among TAVI patients. An average S' below 6.5 cm/sec best defines clinically meaningful reduced longitudinal systolic function and may aid clinical risk stratification in these patients.

Change and impact of left ventricular global longitudinal strain during transcatheter aortic valve implantation

BACKGROUND

Although transcatheter aortic valve implantation (TAVI) is a safe and effective treatment for aortic stenosis, it still carries some risks, such as valve leaks, stroke, and even death. The left ventricular global longitudinal strain (LVGLS) measurement may be useful for the prediction of adverse events during this operation.

AIM

To explore the change of LVGLS during TAVI procedure and the relationship between LVGLS and perioperative adverse events.

METHODS

In this study, 61 patients who had undergone percutaneous transfemoral TAVI were evaluated by transthoracic echocardiography. Before surgery, data on left ventricular ejection fraction (LVEF) and LVGLS were collected separately following balloon expansion and stent implantation. Difference in values of LVGLS and LVEF during preoperative balloon expansion (pre-ex), preoperative stent implantation (pre-im) and balloon expansion-stent implantation (ex-im) were also examined. Adverse events were defined as perioperative death, cardiac rupture, heart arrest, moderate or severe perivalvular leakage, significant mitral regurgitation during TAVI, perioperative moderate or severe mitral regurgitation, perioperative left ventricular outflow tract obstruction, reoperation, and acute heart failure.

RESULTS

The occurrence of perioperative adverse events was associated with differences in pre-ex LVGLS, but not with difference in pre-ex LVEF. There were significant differences between pre-LVGLS and ex-LVGLS, and between pre-LVGLS and im-LVGLS (P = 0.037 and P = 0.020, respectively). However, differences in LVEF were not significant (P = 0.358, P = 0.254); however differences in pre-ex LVGLS were associated with pre-LVGLS (P = 0.045). Compared to LVEF, LVGLS is more sensitive as a measure of left heart function during TAVI and the perioperative period. Moreover, the differences in LVGLS were associated with the occurrence of perioperative adverse events, and changes in LVGLS were apparent in patients with undesirable LVGLS before the surgery. Furthermore, LVGLS is useful to predict changes in cardiac function during TAVI.

CONCLUSION

Greater attention should be paid to the patients who plan to undergo TAVI with normal LVEF but poor LVGLS.

Transcatheter Aortic Valve Implantation: The Evolving Role of the Radiologist in 2021

BACKGROUND

 Transcatheter aortic valve implantation (TAVI) has gained worldwide acceptance and implementation as an alternative therapeutic option in patients with severe aortic valve stenosis unable to safely undergo surgical aortic valve replacement. This transformative technique places the radiologist in a key position in the pre-procedural assessment of potential candidates for this technique, delivering key anatomical information necessary for patient eligibility and procedural safety. Recent trials also provide encouraging results to potentially extend the indication to patients with safer risk profiles.

METHOD

 The review is based on a PubMed literature search using the search terms "transcatheter heart valve", "TAVI", "TAVR", "CT", "imaging", "MR" over a period from 2010-2020, combined with personal comments based on the author's experience.

RESULTS AND CONCLUSION

 CT plays a prominent role in the pre-procedural workup, delivering as a true 3D imaging modality optimal visualization of the complex anatomy of the aortic root with simultaneous evaluation of the patency of the different access routes. As such, the contribution of CT is key for the determination of patient eligibility and procedural safety. This input is supplementary to the contributions of other imaging modalities and forms an important element in the discussions of the Heart Valve Team. Knowledge of the procedure and its characteristics is necessary in order to provide a comprehensive and complete report. While the role of CT in the pre-procedural evaluation is well established, the contribution of CT and MR and the clinical significance of their findings in the routine follow-up after the intervention are less clear and currently the subject of intense investigation. Important issues remain, including the occurrence and significance of subclinical leaflet thrombosis, prosthetic heart valve endocarditis, and long-term structural valve degeneration.

KEY POINTS

  · CT plays a crucial role in evaluating transcatheter heart valve candidates. · Evaluation must include the dimensions of the aortic root and access paths. · The exact post-procedural role of CT and MRI has not yet been determined..

CITATION FORMAT

· Salgado R, El Addouli H, Budde RP. Transcatheter Aortic Valve Implantation: The Evolving Role of the Radiologist in 2021. Fortschr Röntgenstr 2021; 193: 1411 - 1425.

Management of aortic stenosis: a systematic review of clinical practice guidelines and recommendations

Multiple guidelines exist for the management of aortic stenosis (AS). We systematically reviewed current guidelines and recommendations, developed by national or international medical organizations, on management of AS to aid clinical decision-making. Publications in MEDLINE and EMBASE between 1 June 2010 and 15 January 2021 were identified. Additionally, the International Guideline Library, National Guideline Clearinghouse, National Library for Health Guidelines Finder, Canadian Medical Association Clinical Practice Guidelines Infobase, and websites of relevant organizations were searched. Two reviewers independently screened titles and abstracts. Two reviewers assessed rigour of guideline development and extracted the recommendations. Of the seven guidelines and recommendations retrieved, five showed considerable rigour of development. Those rigourously developed, agreed on the definition of severe AS and diverse haemodynamic phenotypes, indications and contraindications for intervention in symptomatic severe AS, surveillance intervals in asymptomatic severe AS, and the importance of multidisciplinary teams (MDTs) and shared decision-making. Discrepancies exist in age and surgical risk cut-offs for recommending surgical aortic valve replacement (SAVR) vs. transcatheter aortic valve implantation (TAVI), the use of biomarkers and complementary multimodality imaging for decision-making in asymptomatic patients and surveillance intervals for non-severe AS. Contemporary guidelines for AS management agree on the importance of MDT involvement and shared decision-making for individualized treatment and unanimously indicate valve replacement in severe, symptomatic AS. Discrepancies exist in thresholds for age and procedural risk used in choosing between SAVR and TAVI, role of biomarkers and complementary imaging modalities to define AS severity and risk of progression in asymptomatic patients.