Percutaneous Coronary Intervention For Acute Myocardial Infarction

Percutaneous Coronary Intervention For Acute Myocardial Infarction

The field of interventional cardiology was launchedover 40 years ago when Andreas Gruentzig performed the first coronaryangioplasty using a primitive balloon catheter. Within a few months, he was doing live demonstration courses. Since then, an ever-expanding collaboration of clinicians, engineers and scientists haveaddressed the many challenges of working within the vascular system to treat coronary artery disease. The development of new devices and techniques as well asnew adjunctive pharmacologic treatments continues to accelerate, making percutaneous coronary intervention (PCI) progressively safer and more applicable to a wider set of clinical scenarios.

The full capability of modern interventional cardiology becomes sharply focused in the treatment of heart attack or acute myocardial infarction (AMI). Immediate PCI has emerged as the best treatment for acute vessel closure, which is the underlying cause of the common type of heart attack called “ST segment elevation myocardial infarction”. The benefit of PCI is very high in this patient group and is largely proportional to the rapidity with which flow is restored in the occluded artery. It has become the standard of care in developed countries to have the culprit artery open within 90 minutes of arrival at the hospital.

In AMI, the race often beginsbefore the patient arrives. An electrocardiogram, done by emergency medical personnel, istransmitted to the emergency physician at a nearby hospital. The diagnosis is made and the catheterization lab staff is activated. In the Seattle area, we enjoy a remarkably efficient and effective emergency medical response system. During transport, the cardiologist, nurses and cathlab technologists spring into action. During nighttime hours, the staff rushes in from home to a pre-set equipment table. After brief evaluation and informed consent in

the emergency department, the patient is swept down the hallto the catheterization laboratory.

Access to the arterial system is achieved, typicallyby ultrasound-guided puncture of the radial artery in the wrist with a fine needle. A catheter is fed up the arm and guided to the entrance of the coronary arteries. X-ray images (fluoroscopy) are made and the acutely blocked artery is identified. If PCI is appropriate, a flexible

and steerable guidewire is threaded carefully through the obstruction. A balloon catheter is passed over the wire into the blocked segment of the artery and the balloon is inflated to push plaque and clot aside. When flow has been reestablished, the patient often feels immediate relief from chest pain.

Once the artery has been initially opened, the vessel is assessed in more detail. Intravascular ultrasound may be used to look frominside the artery, through the wall to see the bulk and composition of the plaque. A stent of appropriate size and length, usually a drug-eluting stent, is deployed within the lesion, permanently embedding it the artery wall.

 

At Overlake, where we started doing primary PCI in AMI more than 30 years ago, our average time to opening the culprit artery is at or below one hour. Some takeunder 30 minutes. We have a robust continuous quality improvement process streamlining each step of the patient’s journeyto keep overall times to a minimum. Recently, we have adapted our process to accommodate the added complexity of the COVID-19 pandemic.

During PCI for AMI, some arterial lesions yield relatively easily. Others may be calcified or tortuous or have unusual branching patterns that make PCI very difficult. A wide array of equipment and techniques have been developed

aid in crossing the lesion, dilating it successfully and keeping it open, while entering and exiting the arterial system safely.

The successful treatment of difficult lesions is enhanced by better wires, guidecatheter extenders, steerable microcatheters and other devices includingdrug-eluting stents. Stents are tiny mesh scaffolds that prop the artery wide open while preserving flow into side branches. They have sophisticated drug delivery systems to inhibit scar tissue formation (neointimal hyperplasia). Stent design continues to improve with better flexibility, thinner struts and better drugs. Successful opening of calcified or fibrous lesions has improved with cutting balloons and rotational atherectomy (a rotating diamond-tipped drill), which soon will be joined by coronary lithotripsy. The safety of procedures is also increasing with a transition to the radial artery approach (entering through the wrist instead of the groin), better medicinesand circulatory support systems for patients with severely impaired heart function. Long term outcomes in patients with AMI have improved with better pharmacology. New medicines prevent clots, restore normal heart pumping function and halt the process of atherosclerotic vessel damage.

During PCI for AMI, the urgency of the situation does not allow for preparation for the specific and uniquechallenges of a patient’s anatomy.In addition to good communication and a well-coordinated process, the experienced interventional cardiologist and his team must have availability of and facility with all these tools. To stand on the shoulders of giants like Gruentzig and the long line of innovatorswho have followed him, all members of the team must be familiar with every page of the playbook.

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