Patients With Low Aortic Valve Gradient May Be Less Likely to Reap TAVR’s Benefits

Low aortic valve gradient and LV dysfunction are commonly seen in patients undergoing TAVR, but only the former is independently associated with poorer outcomes in the first year following the procedure, an analysis of the Transcatheter Valve Therapy (TVT) Registry shows.

“These findings suggest that low aortic valve gradient (but not impaired left ventricular function) is an important factor to consider when evaluating the risks and benefits of TAVR for individual patients,” lead author Suzanne Baron, MD (Saint Luke’s Mid America Heart Institute, Kansas City, MO), told TCTMD in an email.

“However,” Baron added, “it is important to note that neither severe left ventricular dysfunction nor low aortic valve gradient should preclude consideration of TAVR.”

She and coauthors note in the May 26, 2016, issue of the Journal of the American College of Cardiology that patients with both severe LV dysfunction and low aortic valve gradient had a 1-year mortality rate of 33%, which is lower than the 50% mortality seen in medically managed patients with aortic stenosis in the PARTNER B study.

Although both impaired LV function and low aortic valve gradient have been associated with worse clinical outcomes in small TAVR studies, none was large enough to examine whether the two factors “are independent of each other or even possibly synergistic in their effect on outcomes,” Baron said.

To explore that issue, she and her colleagues looked at data on 11,292 patients who underwent TAVR between November 9, 2011, and June 27, 2014, and were included in the Society of Thoracic Surgeons/American College of Cardiology TVT Registry. Information from the registry was linked to Medicare administrative claims data.

Gradient, LV Function Act Independently

The researchers divided patients into three groups according to LVEF: severe dysfunction (< 30%), mild-to-moderate impairment (30% to 50%), and preserved (> 50%). Aortic valve gradient was deemed low (< 40 mm Hg) or high (≥ 40 mm Hg).

Median gradient was lowest in patients with severe LV dysfunction, and median LVEF was lower in patients with low gradient.

Patients with LV dysfunction and low aortic valve gradient had longer lengths of stay and tended to have higher in-hospital mortality. Through the first year of follow-up, both severe LV dysfunction and low gradient were associated with greater risks of mortality and recurrent heart failure.

Rates of death and recurrent heart failure were higher in patients with low gradient within each LVEF group. Thus, patients with preserved LV function and high gradient had the best outcomes (23.65% mortality and 11.2% recurrent heart failure) and those with severe LV dysfunction and low gradient had the worst (33.1% and 23.6%, respectively).

On multivariate adjustment, however, only low aortic valve gradient was tied to higher mortality (HR 1.21; 95% CI 1.11-1.32) and recurrent heart failure (HR 1.52; 95% CI 1.36-1.69); the relationships with LVEF were no longer significant.

LV dysfunction did, however, influence the degree of improvement in health status after TAVR, with greater gains on the Kansas City Cardiomyopathy Questionnaire seen in patients with the most severe impairment at baseline.

LV Function Results ‘Make Sense’

Baron said that the lack of an independent association between baseline LV function and clinical outcomes “makes sense from a physiologic standpoint.”

“It is well known that reduced LVEF can often improve after successful TAVR and this is likely related to the relief of valvular obstruction,” she said. “On the other hand, a low aortic valve gradient is more likely a reflection of reduced flow across the aortic valve, which suggests some form of intrinsic myocardial dysfunction. This is consistent with other studies, which have shown that a low-flow state is an important predictor of worse long-term outcomes.”

In an accompanying editorial, Philippe Pibarot, DVM, PhD (Québec Heart and Lung Institute and Laval University, Quebec, Canada), and John Webb, MD (University of British Columbia, Vancouver, Canada), said the study “further emphasizes the importance of considering the gradient and LVEF in the risk-stratification process of patients being candidates for TAVR.”

The main strength of the study, they say, is the large number of real-world patients that were included. But, they add, there were some limitations, including the lack of core lab adjudication for the echocardiography data, the lack of some important information in the registry, including stroke volume, and the lack of a comparison with patients undergoing either surgery or medical management.

They agree with the authors that neither low aortic valve gradient nor LV dysfunction should disqualify a patient from undergoing TAVR, and that both variables should be considered when making a decision about an individual patient’s risk.

“The information about gradient, [aortic valve area], flow, and LVEF is available from the routine Doppler echocardiographic examination and should be systematically integrated in the risk stratification process of patients with aortic stenosis being considered for AVR,” they say. “The presence of a low gradient, low LVEF, and/or low flow should not preclude the consideration of TAVR or [surgical valve replacement], but it should be interpreted as a marker for higher risk of procedural and postprocedural complications and adverse events.

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• LV Flow After TAVR Predicts Late Mortality