Cardiac Updates

MY APPROACH TO TREATMENT OF HEART ATTACK 2010

We all fear the word heart attack for it is one of the leading killers of both men and women all around the world. But fortunately, today there are excellent treatments for heart attack that can save lives and prevent diabities & death. At the onset of a heart attack, what is most important is the first 1 hour that is termed "the golden hour" by doctors.

Traditionally, when a person suffers from a heart attack, the doctors perform an angioplasty to surgically open up the blockages and restore normal blood flow. But in a city like Mumbai, a typical scene would involve the family calling up an ambulance and taking the patient to a renowned hospital that may be very far from the house, So by the time the patient, reaches the hospital and the surgeons prepare themselves for surgery that golden period of treatment is already gone leaving behind a heart that is damaged as much as 80% which not only decreases the rate of survival but also seriousily affects the 1 year mortality rate of the patient.

But today there is a life savior in the form of clot busters that are medicines that can be administered within that 1 hour period in a local hospital or in the ambulance while going to a good hospital. It works by dissolving the clot in the coronary artery thus preventing much damage to the heart thereby buyinh some for the angioplasty to be performed in the hospital/ This treatment is called thrombolysis and the benefir recorded is closed to 80%.

Research has come up with some starting statistics:

• 68% of people who suffer from heart attacks have blockages less than 50%
• Mortality rates have come down to 6.5% from 30% after thrombolytic therapy
• Angioplasty stent within 6 hour of lytic thrombolysis is the new Pharmaco Invasive Approach 1 year mortality has come down to 3.2% from 15% with this approach.

A heart attack occurs as a result of a condition called coronary artery disease (CAD) where the blood flow to a certain section of the heart muscle gets blocked. Death occurs because of damage caused to the section of heart muscle due to lack of oxygen. Hence it is critical to be treated within the golden hour to save as much of the heart tissue is possible in rder to not only save the patient's life but also extend his lifespan after the attack.

TRANSCATHETAR AORTIC VALVE IMPLANT

Design of Sapien XT valve and technical tips - By Dr Shahid Merchant 

Introduction : Transfemoral aortic valve implantation (TAVI) may offer clinical benefit to patients not well suited to conventional surgery. New developments in delivery systems and valve technologies make the procedure safer, thereby paving the way for a broader application of Transfemoral aortic valve implantation.
Patients with severe symptomatic aortic stenosis are eligible for transarterial aortic valve replacement if the risk of conventional open-heart aortic valve replacement is considered excessive by a consensus group of cardiogists and heart surgeons. A minimal femoral arterial diameter of 7 mm for the 22 F and 8 mm for the 24 F Retroflex 3 system and 6 mm for the 18 F and 6.5 mm for the 19 F Nova flex system is required.

Procedure : is done under local anaesthesia and mild sedation. A percutaneous femoral arterial sheath allows introduction of the delivery system into the descending aorta. Flexion of the delivery catheter tip facilities atraumatic passage through the aortic arch and stenotic native valve. The delivery catheter is withdrawn to the ascending aorta to fully expose the deployment balloon during expansion. The valve is deployed during rapid pacing. Finally the delivery system is retrieved and femoral access site closed either utilizing previously inserted percutaneous sutures (ProGlide TM Prostar ) or by surgical cutdown.

Sapien XT valve : The valve consists of bovine pericardial leaflets, a cobalt-chromium frame and a sealing cuff on the inflow aspect of the stent to prevent paravalvular regurgitation. The bovine pericardium utilized undergoes a proprietary anti-calcification treatment (Thermafix Tm ).
New scallop-shaped leaflets are attached to the frame in a crown-like manner. The redesigned frame incorporates a more open design and a reduction in strut thickness. Stainless steel utilized in the SAPIEN valve is now replaced with a stronger cobalt-chromium alloy.
The design and the material allow for tighter crimping of the valve, without loss of stability or radial force. The SAPIEN XT aortic valve is available in four sizes: 20, 23, 26, and 29 mm external diameter valves. It is slightly longer that the previous SAPIEN valve.

Novaflex delivery system : The system allows for a reduction in sheath size to 18 French (for the 23 mm valve; 19 French for the 26 mm valve). The smaller diameter allows use in patients with smaller diameter ilofemoral arteries: 6 mm for the 18 French and 6.5 mm arterial diameter for the 19 French systems.
The delivery catheter incorporates an outer deflectable catheter and an inner balloon catheter with a tapered crossing tip. The valve itself is crimped on the inner catheter proximal to the inflatable balloon. This reduces the maximal diameter of the delivery catheter and allows for a reduction in sheath size. Once the delivery catheter and prosthesis have been passed through the femoral sheath, the inner balloon catheter is withdrawn back into the outer catheter while maintaining wire position. The outer catheter then advances the prosthesis distally on the inner catheter shaft and onto the balloon. Optimal alignment of the stent on the balloon is indicated when the frame is positioned between the two fluoroscopic markers. Imaging in a fluoroscopic view perpendicular to the markers is important for accurate positioning. Advancing the prosthesis too distally is prevented by a slightly larger distal tip of the balloon catheter. Fine adjustment is achieved by turning a valve alignment wheel situated on the handle of the delivery system.
Balloon expansion generally begins distal (ventricular) to the prosthesis first, followed by expansion proximal (aortic) to the prosthesis and finally by expansion of the central portion of the balloon. The result is initial expansion of the prosthesis within the left ventricular outflow tract (LVOT).

SAPIEN XT valve on the Novaflex delivery system : This allows a further reduction in internal sheath diameter to 18 French and 19 French, respectively. The absence of major vascular complications and major bleeds is encouraging.
The new design tends to result in balloon expansion being initiated distally (ventricular). As the prosthesis expands distally, it first contacts the outflow tract, rather that the leaflets. Subsequently, proximal (aortic) expansion is less likely to result in movement in the direction of blood flow and the native leaflets. Presumably more rapid balloon inflation due to the larger inflation lumen helps.