Affiliated interventional cardiologists with the Memorial Hermann Health System Heart & Vascular Program in Houston are now routinely performing percutaneous coronary interventions for patients with chronic total occlusions, or CTOs. The comprehensive program offers patients access to a multidisciplinary team, research, cutting-edge, evidence-based approaches, and a full spectrum of therapies. The minimally invasive CTO procedures are being offered to symptomatic patients who have either failed surgery or are not candidates for coronary bypass. Started 4 years ago, the Memorial Hermann CTO program has become the busiest CTO program in South Texas, each year performing over 250 CTO procedures on patients referred from across the Greater Houston area, Texas and the United States.
Affiliated interventional cardiologist Salman Arain, MD, associate professor of interventional cardiology at McGovern Medical School at UTHealth Houston, who specializes in treating CTOs and performing other complex and high-risk interventional procedures (CHIPs), answers frequently asked questions about the CTO program and the procedure.
What is chronic total occlusion (CTO)?
A chronic total occlusion is defined as an artery which has been closed for at least 3 months. Coronary CTOs are typically caused by slow progression of atherosclerosis, and as many as 30 percent of patients referred for coronary angiography have a previously undiagnosed occlusion. Occasionally, CTOs may result from a missed myocardial infarction.
What are the usual symptoms of coronary CTO?
The most common symptoms of CTO are exertional fatigue and shortness of breath. Whereas patients with a stenosis often present with chest discomfort—either chest tightness or chest pressure—patients with a CTO do so less frequently because many have developed collaterals from other arteries.
Who is a good candidate for CTO intervention?
Patients who benefit the most from CTO intervention are those who have lifestyle limiting symptoms despite optimal medical therapy. So, for example, patients with CTOs who can run a marathon and go hiking probably do not need CTO intervention.
Most patients who are treated at our program fall into one of two categories: Either they are patients with a single-vessel CTO but not enough disease elsewhere to qualify for coronary bypass, or they are bypass patients whose grafts are failing or have failed. Many of the patients in the latter category have CTOs that are amenable to revascularization. This is often a safer and more durable solution than treating the diseased graft or re-do bypass surgery.
Why not just perform another bypass?
There are several reasons why a re-do coronary bypass is often not recommended. Many of these patients are older than they were at the time of the first bypass, increasing the clinical risk of complications after an operation. Often, they still have one or two functioning grafts as well as extensive intra-thoracic scar tissues related to the healing of the chest wall. Both add to the technical complexity of a repeat procedure. Another consideration is that patients may not have as many veins left for grafts, particularly if they have also had prior lower extremity bypass surgery. A CTO intervention allows patients to be treated successfully while avoiding the risks of another major surgery.
How does the interventional treatment of a CTO differ from typical angioplasty?
The techniques we use to revascularize CTOs are based on the same principles of angioplasty that we use to treat stenotic arteries. The objective is to cross the occlusion with a wire, dilate it using balloon angioplasty and place a stent. However, these procedures require extensive planning and differ from typical angioplasty in several respects:
Dual angiography. We obtain arterial access at two locations—either the wrists or the groins, or a combination of the two. This allows us to engage both the left and right coronary systems and perform simultaneous angiography. The dual angiogram thus obtained allows us to define the length and direction of the occlusion and to the identify specific features, such as degree of calcification. Once the intervention is underway, dual angiography allows us to monitor our progress in crossing the CTO and make the necessary adjustments.
Hybrid approach. Whereas angioplasty is typically only performed in the antegrade direction (proximal to distal), an intervention for a CTO may require a retrograde approach, from the distal segment of the artery. This becomes necessary when the antegrade approach is unsuccessful or not possible. CTO operators are often adept at using collaterals within the muscle (septal) or along the surface (epicardial) to approach the occlusion from the opposite direction. This requires specialized wires, dedicated microcatheter and years of practice to accomplish.
Specialized equipment. There are several different techniques for entering and exiting CTOs. Often a combination of two is required for a successful crossing. Many different tools have been developed to make these processes safe and effective. Our lab is fully equipped with many such devices to ensure the maximal chances of success.
What is the process for obtaining a CTO intervention at Memorial Hermann?
For me, every CTO intervention begins with a face-to-face office or in-hospital visit with the patient and his/her family. I like to meet patients first to understand their symptoms and to confirm that they truly have a CTO that needs to be treated. This meeting also allows me to review their coronary angiogram(s), understand their expectations and discuss the risk, benefits and alternatives to percutaneous intervention. Often, I will make a diagram of the coronaries for the patient at this meeting and use it to formulate a strategy and explain it to them. It is important for patients to understand that success is not always guaranteed, that sometimes it may take two procedures to successfully treat the CTO. Once I have answered the patient’s questions, we pick a date for the procedure.
Most patients spend the night in the hospital. However, they may need to stay a few extra nights for additional observation in some cases. Patients may go home the same day if the procedure is uncomplicated and there is someone to take care of them at home.
What was the impetus for creating the Memorial Hermann CTO program?
Houston is the fourth largest metropolitan area in the United States, and until 4 years ago it was one of the few major cities without a dedicated CTO program. Many cardiologists, cardiothoracic surgeons and patients were unaware that it is possible to treat CTOs non-surgically, but the CTO program at Memorial Herman is slowly changing that. There continues to be a large unmet need for CTO operators in Houston because patients are still being sent to other states for an intervention. Many physicians are unaware that we can do it all here or that we take on even the most complex coronary cases. We encourage referring interventional cardiologists to participate with us if possible. The goal of our program is to improve the health of the community, in keeping with Memorial Hermann’s vision to create healthier communities, now and for generations to come.