Sandbox:TAVI

Overview

Until recently, aortic valve replacement (AVR) was the only effective treatment for severe symptomatic aortic stenosis. Global aging has raised concerns about safety and possibility of surgical procedure in old patients with associated co-morbidities. Transcatheter aortic valve replacement (TAVR) created a new era of safety for this population and enabled physicians to replace the stenotic valve with more certainty. In Transcatheter Aortic Valve Replacement (TAVR) also known as Percutaneous Aortic Valve Replacement (PAVR), a synthetic valve is advanced to the heart through a small hole made in groin. This procedure is similar in its mechanism to the insertion of a stent, or performing balloon angioplasty albeit with much larger equipment. Traditional aortic valve replacement is an invasive surgical procedure, with considerable mortality and morbidity, especially in more fragile patients. In the newly developed TAVR procedure, the dysfunctional aortic valve is replaced percutaneously, which obviates the need for open heart surgery.
Patient selection, selecting the appropriate imaging modality, preprocedure evaluation, selecting the appropriate valve type and valve size, post procedure complications and long term follow up are the main area of focused importance.
We will describe these factors based on the recent expert consensus for TAVR procedure.

Definition

The most important step is to define the severity of AS and appropriate patient that need TAVR. Severe symptomatic (Stage D) AS is considered as TAVR candidate.

Abbreviations: ΔP: mean gradient, Vmax: maximum aortic velocity, AVA: aortic valve area. AS: aortic stenosis, AR: aortic regurgitation.

Severe symptomatic AS (stage D)
STAGE	DEFINITION	SYMPTOMS	VALVE ANATOMY	VALVE HEMODYNAMICS	HEMODYNAMIC CONSEQUENCES
D1	Symptomatic severe high-gradient AS	Exertional dyspnea or decreased exercise tolerance Exertional angina Exertional syncope or presyncope	Severe calcification or congenital stenosis with severely reduced opening	Vmax ≥ 4 m/s or mean ΔP ≥ 40 mmHg AVA ≤ 1.0 cm² but may be larger with mixed AS and AR	LV diastolic dysfunction Left ventricular hypertrophy May present with pulmonary hypertension
D2	Symptomatic severe low-flow/low gradient AS with reduced LVEF	Heart failure Angina Syncope or presyncope	Severe calcification or congenital stenosis with severely reduced leaflet motion	AVA ≤ 1.0 cm² with resting aortic Vmax < 4 m/s or mean ΔP ≥ 40 mmHg Dobutamine stress echo shows AVA ≤ 1.0 cm² with Vmax ≥ 4 m/s at any flow rate	LV diastolic dysfunction Left ventricular hypertrophy LVEF <50%
D3	Symptomatic severe low gradient with normal LVEF	Heart failure Angina Syncope or presyncope	Severe calcification with severely reduced leaflet motion	AVA ≤ 1.0 cm² with Vmax < 4 m/s or mean ΔP ≤ 40 mmHg AVA ≤ 0.6 cm² Stroke volume index < 35 mL/m²	Increased LV relative wall thickness Small LV chamber with low stroke volume Restrictive diastolic filling LVEF ≥ 50%

Comparing TAVR and SAVR

Surgical Aortic Valve Repair (SAVR) is the traditional way of treating a stenotic aortic valve. In the last decade TAVR has emerged as a viable option for patients at high surgical risk or at high risk for post-surgical complications. The most current 2014 AHA/ACC guideline for management of patients with valvular heart disease recommends the following:

Class of Recommendation	Recommendation	Evidence Level
Class I	"SAVR is recommended in patients who meet an indication for AVR with low or intermediate surgical risk"	A
Class I	"For patients in whom TAVR or high-risk SAVR is being considered, members of a Heart Valve Team should collaborate to provide optimal patient care"	C
Class I	"TAVR is recommended in patients who meet an indication for AVR for AS who have a prohibitive surgical risk and a predicted post-TAVR survival >12 months"	B
Class IIa	"TAVR is a reasonable alternative to SAVR in patients who meet an indication for AVR and who have high surgical risk"	B
Class IIb	"Percutaneous aortic balloon dilation may be considered as a bridge to SAVR or TAVR in severely symptomatic patients with severe AS"	C
Class III: No Benefit	"TAVR is not recommended in patients in whom existing comorbidities would preclude the expected benefit from correction of AS"	B

In recent years, terminology has arose to define patients who qualify for TAVR as "inoperable patients" who are at >50% risk of mortality at 30 days after a potential SAVR procedure. There is much debate regarding the subjective nature of defining a patient as "inoperable"; however, the heart valve team should collaborate to determine the optimal procedure for the patient.
TAVR has demonstrated up to a 20% risk reduction in all-cause-mortality at 12 months which is sustained for up to 5 years post-procedure, when compared to SAVR. In high risk patients such as the elderly and those with a NYHA III or IV functional status, TAVR showed non-inferiority to the traditional SAVR procedure and regardless of the procedure undertaken, patients maintained a NYHA I or II functionality for up to 5 years post-procedure.

It is noteworthy to say that TAVR is associated with a significant and sustained reduction in risk of ischemic stroke for 30 days and up to 2 years after the procedure compared to surgery. Nevertheless, SAVR continues to play a role in patients who require an aortic valve replacement with lower surgical risk.