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Coronary Chronic Total Occlusions
Chronic Total Occlusions are where a coronary artery has been occluded for more than 3 months. The cause tends to be a combination of both severe progressive atherosclerosis together with super-added arterial thrombosis. This means CTOs can form both silently or after episodes of progressive chest pain or angina.
CTOs can be a cause of angina, a recurrent sensation of chest heaviness on exertion. There may be signs seen on an electrocardiograph or echocardiogram. They may be suggested by CT-Angiography but they are definitively diagnosed using invasive angiography. A vessel may be deemed to be a CTO based upon it’s angiographic appearance. In some cases, where there is doubt, it may be gently probed with a hair-thin intracoronary wire; if there is significant resistance to it’s passage, then a CTO is more likely.
In most cases, patients with CTOs will have collateral arterial growth. Small blood vessels will grow from the remaining arteries. Often these vessels can provide sufficient supply to keep the heart muscle alive. In some cases, the collaterals are sufficient to keep symptoms of angina to a minimum. However, in very active patients, collaterals may not offer sufficient blood flow to minimise angina.
Patients with CTOs will undergo a number of assessments. Once identified, it is common to assess the heart muscle for viability. This means specifically assessing the function of the part of the heart supplied by the blocked artery. In some cases, the heart muscle may be irrevocably damaged and there is little to no value in attempting to open the blood vessel. In other cases, the heart muscle is still functioning but may be hibernating. In these cases, opening the CTO may improve anginal symptoms and restore function in the hibernating segments. Patients may undergo specialist Cardiac MRI or Position Emission Tomography testing to assess myocardial viability.
Treatment of CTOs involves a careful step-wise approach. All patients with CTOs should be on optimal medical therapy with tablets that have been shown in research studies to improve symptoms. In those patients with unacceptable anginal symptoms or certain changes on non-invasive testing, your Cardiologist may offer an attempt to open the CTO. This is typically a much more complex procedure than other PCI procedures. The procedure can require an attempt to pass increasingly sharp wires through the occlusion (antegrade) or attempt to pass wires through collateral branches (retrograde). Both antegrade and retrograde approaches may be needed
CTO procedures require specialist training and more than one Consultant may be present to perform the procedure. Multiple tubes or catheters may be required. These procedures are typically longer than more routine PCI procedures and have a higher risk. Your Cardiologist will discuss the precise risk for your particular CTO. In some cases, patients require more than one procedure to completely open the occluded vessel.