Caroline Cristofaro investigates percutaneous coronary interventions (PCI) in the treatment of complete total occlusions.
Cardiology is, like most specialties in medicine, constantly evolving, and at the heart (pun intended) of these developments is the angioplasty. The formation of plaque and clogging of the vessels around the heart is becoming a common problem in today’s society and, with medical technology constantly changing and improving, less invasive and more successful procedures are being developed. Completely occluded arteries have long been treated with open heart surgery, a very invasive procedure, but in the past couple of decades, the angioplasty is evolving to be able to treat more serious pathologies in a much less invasive manner (Shah 2011). With the abilities of cardiologists growing and technology evolving with them, will cardiac surgeons find their number of cases dwindling and ultimately “go out of business”?
The angioplasty, commonly known as a percutaneous coronary intervention (PCI), is a procedure used to open up blocked arteries. However, a more in-depth explanation is in order. During a PCI procedure, a diagnostic angiography is also performed prior to the actual opening of the blocked vessels. This is done by first obtaining access through the right radial artery (preferably), or right femoral (used when the patient has difficult to navigate collateral vasculature); in rare cases, the brachial artery may also be used. After initial access is established, a guide catheter is passed through the succeeding arteries until the coronary arteries are reached. An intracoronary injection of contrast combined with fluoroscopy is used to enable the interventional cardiologist to visualize both the vasculature (as anatomical variations are quite common) and also the nature of the arterial occlusion(s) [(Grech 2003). At this point in time, the cardiologist decides where the optimal placement of a stent would be. Before proceeding any further, it is of the utmost importance to possess the knowledge of what exactly a stent is and what it can do, as the innovation and implementation of stenting is regarded as an important, if not the most important, step in cardiology. A stent is a mesh tube made of metallic alloys, which can be bare metal or drug-eluting, that is implanted within an artery to induce revascularization (Shoulders-Odom 2008). A balloon is often used before placing a stent (known as pre-dilation) and after (known as post-dilation) to aid in clearance of the vessel – the procedure is therefore also referred to as a balloon angioplasty.
After the procedure, the patient’s angina symptoms are nearly completely relieved, and patients are discharged home after only a few hours in a coronary care unit (Shoulders-Odom 2008). Until the mid-1970s, PCI procedures were not as commonly used as the tried and tested method of coronary artery bypass grafting (Shah 2011). However, with techniques improving, and radical new stents being developed, PCIs are now being used as alternatives for treating patients suffering from a chronic total occlusion (CTO), which were previously only treated with CABG.
A CTO is the complete blockage of an artery in which an atherosclerotic plaque has been sitting for a minimum of three months (Shah 2011). Evidently this poses a severe problem to the patient, as a portion of the heart will not be receiving an adequate supply of blood – which could result in a myocardial infarction. As aforementioned, CABG was the method of choice to treat this condition, but a PCI designed to treat this condition may be a less invasive and less traumatic option that is being considered. It begs the question: how on earth is a guide catheter pushed through a 100% occluded, tough, often even calcified, plaque without a dissection (accidental tearing of the tunica intima) occurring? There are two main answers to this question according to the study by Shah. Firstly, some interventional cardiologists choose to focus on treating CTOs, and are thus more skilled and competent in this area. Secondly, the technology and equipment used in cardiology are adapting rapidly, especially those used in the treatment of CTOs. In Shah’s investigation, the development of contrast-induced nephropathy due to extended fluoroscopy times was a critical problem in this case as patients undergoing a PCI for a CTO has, on average, double the fluoroscopy time.
To counter this problem, patients are now referred to pre-procedure computed tomographic angiography. This type of imaging enables the cardiologist to visualise the entire course of the diseased vessel. This visualization is crucial in obtaining information on the length of the occlusion, and also greatly decreases the risk of dissections during the procedure as different entry routes to the CTO can be identified (Shah 2011). New guide catheters that have a hydrophilic coating are specifically used when treating CTOs with PCI. This coating enables the wire to find microchannels within the CTO to obtain access to the distal vessel, as researched by Shah. Cardiologists have also developed their techniques by passing through collateral vessels to access the distal end of the CTO, and subsequently accessing the proximal end, which is often easier to cross. These novel developments, specifically tailored to the treatment of CTOs, have significantly increased the procedural success of CTOs treated with PCIs. Since angioplasties were first used to attempt to treat CTOs, the success rate has increased from 51% to 70% in recent years. The approximate 20% increase is promising for the continued use of angioplasty procedures to treat a patient’s CTO [(Shah 2011)].
Dr. Errett, a cardiac surgeon at St. Michael’s Hospital in Toronto, described this practice as the “Cardiologists trying to put us [Cardiac Surgeons] out of business”. The CABG procedure is mainly used to treat patients suffering from CTOs and multivessel CAD, and so the overlap between these two fields is growing. Whilst the statistics for CTO PCIs are promising, they cannot compete with the ~97% success rate of PCI treating non-CTO lesions (Shah 2011) or the ~97% success rate of CABG (Hawkes 2006). Cardiologists are also limited in the severity of CTO they are able to treat. The CTO lesion must be in either the right coronary artery or in the left coronary artery after the bifurcation of the left main coronary artery; the case is otherwise too severe and the patient will be referred for CABG (Shah 2011). Although a patient having undergone a successful PCI for CTO has a greater decrease in recurrent angina and improvement in left ventricular function (Shah 2011), CABG is still, for the moment, the preferred treatment for patients with any condition involving CTOs simply due to its superior rate of successful procedures.
In conclusion, a percutaneous coronary intervention is now regularly used to treat patients with one CTO. However, there are significant limitations to PCIs treating CTOs as well. Chief amongst them is that the patient can only be suffering from 1 CTO lesion without significant calcification (Grech 2003) and cannot be affecting the left main, else the PCI procedure would be too lengthy, use too many supplies, and be too risky (dissection, bleeding, CIN, etc.) (Shah 2011). Cardiac Surgeons are well versed in the treatment of CTOs and still hold the upper hand in terms of successful treatment. It looks like cardiac surgeons aren’t going out of business just yet…
Grech, D.E. 2003. Percutaneous coronary intervention. II: The procedure. BMJ 326:1137. doi: 10.1136/bmj.326.7399.1137 [Accessed 21.10.14]
Hawkes, A.L., Nowak, M., Bidstrup, B., Speare, R. 2006. Outcomes of coronary artery bypass graft surgery. Vascular Health and Risk Management 2(4): 477-484. Available: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1994021/?report=classic [Accessed 21.10.14]
Shah, P. 2011. Management of Coronary Chronic Total Occlusion. Circulation 123: 1780-1784. doi: 10.1161/CIRCULATIONAHA.110.972802 [Accessed 21.10.14]
Shoulders-Odom, B. 2008. Management of Patients After Percutaneous Coronary Interventions. Critical Care Nurse 28(5):26-40. Available: http://ccn.aacnjournals.org/content/28/5/26.full [Accessed 21.10.14]