Aortic and Pulmonic Balloon Valvuloplasty

Patient Preparation and Access

Over 50% of BAVs at MHI are performed electively by way of outpatient admission. Patients are pretreated with 325 mg of aspirin. A large-bore peripheral intravenous (IV) line and usually a Foley catheter are placed before transfer to the cardiovascular laboratory, especially in patients in whom postprocedure diuresis is anticipated. An intraaortic balloon pump (IABP) should be available in the room for patients who are hemodynamically unstable or those with left ventricular ejection fraction (LVEF) less than 30%. Defibrillation patches are placed in the lateral chest positions where they will not interfere with imaging. The procedure is carried out under conscious sedation using IV midazolam and fentanyl.

Both right and left groins are prepped. The authors most commonly use just the right side for arterial and venous access. Six-French femoral arterial and 8F femoral venous sheaths are placed when the patient is under local anesthesia. Care is taken to document appropriate landmarks to ensure arterial access through the anterior wall of the common femoral artery. After confirming common femoral artery access with a contrast injection, the arterial access site is preclosed using two 6F ProGlide devices (Abbott Vascular, Abbott Park, Ill.). Sutures are deployed sequentially at 90-degree angles to each other at the 10 o’clock and 2 o’clock positions and draped to either side with Kelly clamps. A 10F to 12F sheath is then exchanged for the initially placed sheath, depending on valvuloplasty balloon type and size. Alternatively, a single 10F Prostar device (Abbott Vascular, Abbott Park, Ill.) can be used. Patients are then given 70 units/kg of unfractionated IV heparin, which is titrated to achieve an activated clotting time (ACT) of 250 to 300 seconds.

Intraprocedural Diagnostic Evaluation

Coronary angiography is performed, most importantly, to rule out critical stenosis of the left main coronary artery before proceeding with BAV. An unprotected critical left main coronary artery, if anatomically suitable, should be stented before performing BAV. Other severe lesions felt to be clinically relevant can be treated safely after BAV as a combined procedure. See the subsequent discussion on combined coronary stenting and BAV.

Right heart catheterization is then performed with a Swan-Ganz catheter (Edwards Lifesciences, Inc., Irvine, Calif.). Given the incidence of disparity in cardiac outputs, the authors perform both thermodilution and estimated Fick outputs for use in the Gorlin formula when calculating the aortic valve area (AVA). The left heart catheterization is performed, and simultaneous left ventricular and aortic pressures using a dual lumen pigtail catheter are recorded to derive the mean valve gradient. Central aortic pressure from the ascending aorta should be sampled to prevent arterial amplification and a delay in the arterial waveform, which is seen when sampling from a peripheral site. It is imperative to place greater emphasis on the aortic valve index than the AVA when making treatment decisions. In large patients, AVA will significantly underestimate the severity of stenosis. A valve index greater than 0.6 cm ² /m ² is severe.

Crossing the Aortic Valve and Guidewire Positioning

Patients undergoing BAV will be heparinized before the aortic valve is crossed. Nevertheless, it is important to routinely wipe wires and flush catheters with heparinized saline every 2 minutes during attempted crossing. Although one’s choice of catheters for crossing the valve is somewhat personal, most operators use 6F Amplatz left (AL; Cordis Corporation; Bridgewater, N.J.) diagnostic catheters to best achieve a coaxial trajectory with a straight wire to access the left ventricle. A preferred choice has been an AL-1; however, an AL-2 configuration, especially in patients with a horizontal root and vertical valve, may be preferred. The authors prefer to attempt crossing in a 20-degree to 40-degree left anterior oblique projection. A brief cine run for two to three cardiac cycles without contrast is first captured for defining the precise location of systolic leaflet separation. The catheter is then positioned within the systolic jet, which is confirmed fluoroscopically by visualizing catheter tip vibration. The softer end of the straight-tip wire is then used to gently probe the valve in the area where leaflet separation was documented. Clockwise and counterclockwise catheter rotations are generally required to fall into the correct anteroposterior plane of the valve orifice. Once the valve is crossed, an attempt to fix the wire in the middle of the ventricular cavity is made, at which point the working view is switched to a right anterior oblique projection for further wire and catheter positioning (Figure 5–2, A-E ) . With the straight-tip wire fixed, the AL catheter is advanced into the left ventricle, avoiding advancement of the catheter tip and wire forcefully into the apex or other endocardial segments. Myocardial perforation can occur in this context. The catheter may be fixed in the mid-left ventricular chamber when removing the guide wire, allowing the broad secondary curve of the AL catheter tip to point back retrograde toward the aortic valve. A 0.035-inch J -tipped exchange wire can then be advanced through the AL catheter and easily draped in a broad curve across the anterior, apical, and inferior wall segments. A dual lumen pigtail catheter is then advanced into the left ventricle over the exchange wire, and simultaneous left ventricular and central aortic pressures are recorded to obtain a mean aortic valve gradient.

Rapid Ventricular Pacing

Rapid ventricular pacing has been invaluable for stabilizing balloon position across the aortic valve during inflation. The marked decrement in forward stroke volume with pacing significantly reduces the likelihood of the balloon being ejected into the aorta. A bipolar pacing lead is positioned in the right ventricle via the right femoral venous sheath, and stable capture thresholds are confirmed. Some operators have reported success in attaching an external pacemaker directly to the left ventricular wire and skin using alligator clips to achieve rapid pacing without the need for a transvenous pacemaker. A brief pacing run is carried out at 180 to 220 beats/min to ensure consistent 1:1 capture without intermittent loss of capture or 2:1 exit block. A drop in systolic blood pressure to less than 50 mmHg also needs to be confirmed with this rapid pacing sequence (Figure 5–3) . In patients with severe left ventricular systolic dysfunction, pacing at add 180 beats/min is often adequate to achieve significant drop in blood pressure. Test runs should be kept to a minimum to avoid provoking a transient decrease in LVEF and more prolonged hypotension. These high pacing rate commands can be given only by pacing from the atrial (not ventricular) connection terminal on the pacing box. A lower rate limit of 60 beats/min is programmed for backup pacing if necessary.

Balloon Selection, Positioning, and Inflation

The authors use an Amplatz Extra Stiff 0.035-inch exchange wire for the balloon valvuloplasty. Before exchanging this wire through the double-lumen pigtail catheter (or other diagnostic catheter) in the left ventricle, a broad loop is shaped in the flexible end either using a dull instrument or finger tips ( Figure 5–4 ). Broader loops should be made for larger left ventricles. The curve is generally begun just proximal to the stiffer shaft transition into the more flexible segment, thereby avoiding a potential acute angled buckle in the wire capable of perforating the ventricle. In a right anterior oblique fluoroscopic projection, the wire is advanced into the ventricle and with the aid of the indwelling pigtail catheter, can be easily draped across the anterior, apical, and inferior wall segments. It is important to preserve this distal wire curve and left ventricular relationship during balloon inflation to avoid left ventricular perforations, which can occur during subsequent balloon inflations if the distal wire tip or sharply angled bend is pointed into the apex or inferior wall (Figure 5–5, A and B ) .

Balloon sizing is generally more aggressive in stand-alone BAV than when predilation is carried out for TAVR. The authors use 4-cm noncompliant aortic balloons (e.g., Z-Med and Z-Med II [B. Braun Interventional Systems, Bethlehem, Pa.]) and generally begin with a balloon diameter-to-annulus ratio of 1:1 in stand-alone cases and 1 to 2 mm less when predilating for TAVR. The Maxi LD balloon (Cordis Corporation, Bridgewater, N.J.) is another popular choice; it is available in 4- or 6-cm lengths with a rated burst pressure of 5 to 6 atm and can be placed through smaller sheaths (8F to 12F) than the Z-Med balloons. More compliant balloons (e.g., Tyshak II [B. Braun Interventional Systems, Bethlehem, Pa.]) have the advantage of being lower in profile, and thus access sheaths ranging from 8F to 10F can be used. The more compliant balloons have less predictable inflation diameters, requiring the operator to use more conservative balloon diameters. In addition, rated burst pressures are just 2 atm or less. With these cylinder-shaped aortic balloons, antegrade migration can occur into the ascending aorta, even with rapid ventricular pacing. It is therefore important to choose a balloon diameter at least 1 to 2 millimeters less than the measured sinotubular junction diameter. Contrast used for balloon inflation is diluted to 1:8 or 1:10 to minimize viscosity and thus inflation/deflation times. The authors use a 60-cc handheld, disposable plastic syringe to inject the dilute contrast. Most balloons are filled using 20 to 30 cc of the dilute contrast. A 10-cc side syringe can be connected to a three-way stopcock on the balloon injection port to achieve more rapid filling or augment inflation volume. After positioning the uninflated balloon markers across the valve, rapid ventricular pacing is initiated. After confirming 1:1 capture and a systolic arterial blood pressure less than 50 mmHg, the balloon is inflated as rapidly as possible by the second operator or technician. The first operator holds the balloon catheter shaft, making adjustments under fluoroscopy to maintain a stable balloon position centered across the valve (Figure 5–6) . The balloon is fully inflated for 2 to 3 seconds before deflation. Arterial pressure is monitored from the femoral arterial sheath side-arm. After balloon inflation, the contrast is aspirated as rapidly as possible, and the balloon pulled promptly back into the aorta. The pacer is not turned off until most of the contrast is removed from the balloon. Generally no more than 2 to 3 inflations are performed with each balloon size in stand-alone BAV. Subsequent inflations are not carried out unless the arterial blood pressure has completely returned to baseline. If necessary, we use 100 to 200 μ of phenylephrine in IV boluses to maintain systolic blood pressures greater than 100 mmHg. If there is difficulty squarely landing the inflated balloon on the valve, more rapid pacing rates may be beneficial, providing 1:1 capture is preserved.

After each set of inflations, the balloon catheter is exchanged for the double-lumen pigtail catheter, and an aortic valve gradient is remeasured. If hemodynamic targets are not achieved, a balloon that is 1 mm larger is used, and further dilations are carried out if the patient’s condition remains stable. Over 90% of the balloon diameters used for aortic valvuloplasty at MHI range from 22 to 25 mm.