Balloon Mitral Valvotomy (BMV) is also known as Percutaneous Transmitral Commissurotomy (PTMC). It is a catheter based method from dilating the stenosed valve in mitral stenosis. The approach is through the right femoral vein. Both femoral vein and artery are cannulated using the Seldinger technique. A pigtail catheter is placed in the root of the posterior sinus in the root of the aorta. The position is confirmed by injecting contrast. This catheter is used as a position guide while puncturing the interatrial septum.
Pigtail catheter positioned in posterior sinus of aortic root.
Confirmed by contrast injection
An 0.032″ straight guidewire is introduced into the right femoral vein and guided into the superior vena cava through the external iliac, inferior vena cava and right atrium. From the superior vena cava, the guide wire is routed to the left brachiocephalic vein. A Mullin’s sheath with dilator is threaded over the guide wire and positioned in the left brachiocephalic vein. The guide wire and dilator are removed and a Brockenbrough needle is introduced into the Mullins sheath. The needle tip is kept about 2 finger breadths inside the sheath, from its tip. The proximal end of the Brockenbrough needle is connected to the pressure monitoring system through a three way stop cock. While monitoring pressure wave form, the Mullin’s sheath – Brockenbrough needle assembly is brought down into the superior vena cava and then into the right atrium gently. As the asssembly descends in the right atrium, slight forward jerks are seen as it reaches the region of the fossa ovalis. The tip of the assembly should be one space below the pigtail tip in left anterior oblique view to ensure that the site is accurate. In right anterior oblique view the tip should be midway between pigtail anteriorly and spine posteriorly. A more anterior puncture can injure the aorta while a more posterior puncture can cause an atrial stitch. Atrial stitch is a puncture of posterior portion of right atrium and left atrium together rather than a septal puncture. Since the needle will traverse the perciardium in between, it will lead to cardiac tamponade when the needle is removed.
Once the puncture site for the septal puncture has been localised, some operators tent the septum and inject a small amount of contrast to verify the position. Once the position of the needle tip in the region of fossa ovalis is confirmed, the needle is advanced under fluroscopic guidance, observing the needle tip pressure. The pressure wave form switches from right atrial pattern to a higher pressure left atrial pattern as soon as the septum is crossed. Left atrial position can be further confimed by withdrawing bright red saturated blood from the needle by aspiration. As a final confirmation, dye can be injected into the left atrium and can be seen swirling inside the left atrium.
Once the needle is safely inside the left atrium, the Mullin’s sheath is advanced over it into the left atrium. Then the needle is withdrawn, and a pigtail wire is introduced into the left atrium through the Mullin’s sheath. The pigtail wire curls in the left atrium with its top portion reaching the roof of the left atrium. Then the Mullin’s sheath is removed and a septal dilator threaded over it. The septal dilator is passed to and fro across the inter atrial septum a couple of times to ensure adequate dilatation of the septal puncture.
Once the dilator is in position, the BMV balloon is checked for proper inflation and deflation with dilute contrast. The volume of contrast used depends on the proposed level of dilatation to be done. Height of the patient in centimeters is divided by ten and then ten is added to it. The figure obtained will give the proposed diameter of the balloon in millimeters. The position of the piston in the syringe when contrast is filled is noted so that in case of any inadvertent contrast leakage from the system, the system can be refilled without taking it out of the system.
The balloon assembly is threaded over the pigtail wire after removing the septal dilator. Once the balloon tip is in the left atrium, the proximal end is unscrewed and the straightener is removed, while gently pushing the balloon into the left atrium so that the tip will curve around the roof of the left atrium. The balloon tip pressure (left atrial pressure) is measured and the pigtail catheter is introduced into the left ventricle to measure the left ventriuclar diastolic pressure. The transmitral gradient is calculated. The the curved stillet is then introduced into the balloon, taking care to see that the tip does not protrude out of the balloon tip and cause injury.
The balloon is gently introduced into the left ventricle. Counterclockwise torque applied to the stillet is useful in guiding the balloon into the left ventricle. A bobbing movement of the balloon catheter tip is noted when the tip approaches the mitral valve. Once it is certain that the tip has crossed the mitral valve into the left ventricle, The balloon is inflated. While inflating, initially the distal portion of the dumb bell shaped balloon gets expanded. Once the distal half is inflated, the balloon is pulled back to hitch the mitral valve and further inflation dilates the mitral valve. Once full dilatation is achieved, the balloon is promptly deflated to avoid compromise of systemic blood flow. The assembly is withdrawn into the left atrium and the stillet is removed.
Distal half of balloon being inflated and tugged against the mitral valve.
Balloon is fully inflated and the waist can been disappearing.
Transmitral gradient is measured to assess the procedure result. If the result is unsatisfactory, a repeat dilatation with slightly increased balloon diameter. Auscultation for reduction of mitral diastolic murmur and absence of mitral regurgitant murmur are routine while assessing the result. If an echo is available in the cathlab, it will be quite useful to assess the result as well as to exclude any pericardial effusion / tamponade.