Should Patients With Stable Coronary Artery Disease Undergo Stent Placement?

Should anyone with obstructive coronary artery disease undergo angioplasty and stent placement?

The answer is, of course, no.

Like everything else in medicine, intervening in a disease process is all about risks vs benefits. The immediate risks of the procedure should be weighed against the patient’s gains from that procedure.

In considering invasive coronary intervention, the degree of symptomatic relief as well as preventing future cardiac events should be weighed against the immediate risks of the procedure. Many trials have tried to identify the patient pools where the benefits of an invasive strategy outweigh the risks.

The recently presented ISCHEMIA trial renewed this discussion regarding the utility of coronary interventions in patients with significant disease. In this trial, presented at the last American Heart Association meeting, patients with stable coronary artery disease were randomized to an invasive strategy with coronary angiography and revascularization (either via stent placement or cardiac bypass surgery) vs Optimal Medical Therapy ( OMT).

After a median of 3.3 years, there was no difference in terms of cardiovascular deaths, heart attacks, heart failure or unstable angina admissions as well as resuscitated cardiac arrests. However, quality of life was shown to be more improved in the invasive treatment arm due to better relief of anginal symptoms.

ISCHEMIA, while a landmark trial, is not the only study showing similarity between OMT and revascularization in patients with coronary artery disease. COURAGE and BARI 2D are two such trials published in the past couple of decades showing similar findings.

There were several criticisms of these trials that resulted in the need for ISCHEMIA. For example, both these trials did not include the new generation of stents.

ISCHEMIA Trial

Also, a significant number of patients enrolled had low burden of ischemia (inadequate blood supply to the heart due to the blockage). Patients with low burden of ischemia are thought to derive less benefit from invasive strategy compared to those with higher degree of ischemia.

Additionally, everyone received cardiac catheterization prior to randomization introducing operator bias in the equation. Keeping the treating physicians blind to the patient’s coronary anatomy (obtained by CT angiography in most) prior to randomization, utilizing new stent designs in the invasive arm, and enrolling only patients with moderate or higher degree of ischemia, the ISCHEMIA trial eliminated some of the concerns raised by the earlier studies.

ISCHEMIA confirmed what most interventional cardiologists already believed. In patients with stable coronary artery disease who do not have high risk features such as left main obstructive disease or very poor heart muscle function (these groups were excluded in the ISCHMIA trial), an invasive strategy alleviates symptoms much better than OMT alone, but it does not give superiority in terms of future deaths or heart attacks.

So, do we have all the answers now based on these results? Should we tell our patients that they only get better symptomatic relief via invasive strategy and nothing else?

The majority of the data available points to the validity of this statement but there remains some unanswered questions. For one, did this study use nuclear or echo imaging as the initial work up for most patients? Nuclear perfusion imaging and stress echocardiography while prevalent are hardly the best tests to define the ischemic burden. Perhaps utilizing more sensitive tests such as PET or FFRCT would better identify patients with higher burden of disease and at higher risk.

Also, as of now we know that patients were randomized based on having more than 50% luminal narrowing on CT angiography. As all interventional cardiologists know, there is a big difference between 50% narrowing and 95%. It is unclear how many patients had FFR (hemodynamic assessment of the blockage) performed at the time of revascularization in ISCHEMIA. No one intervenes on a 50% narrowing without functional data.

Studies such as FAME have shown that identifying lesions with hemodynamic significance at the time of the angiography and intervening on them only will provide patients benefit from future events.

The exact severity of coronary artery disease on CTA and its correlation to the stress imaging studies are unknown since investigators were blinded to the CT results. We also don’t know how many patients in the invasive arm had complete revascularization. Lack of complete revascularization (leaving some of the narrowing untreated at the time of the invasive procedure) could explain absence of superior benefit with the invasive arm.

Upcoming release of further data from the trial will shed light on some of these concerns.

In summary, many patients might benefit from coronary intervention and stent placement on top of OMT. However, this benefit comes from symptomatic relief. So far, there is little data to suggest coronary stent placement protects most stable patients (patients with high risk characteristics excluded) from future cardiac events.

Whether to proceed with coronary intervention or continue with OMT should be based on in-depth discussion between the patient and their treating physicians. Severity of patient symptoms, compliance with medications and understanding of the data by the patient are essential in shared decision making.

Additionally, it is essential that the patient’s work up not stop at perfusion nuclear imaging, given patients with high risk anatomical findings on the follow up CTA were excluded from ISCHEMIA. It would be catastrophic to miss a patient with left main disease (about 5% of screened patients in the trial).

Perhaps a more sensitive test to identify patients with high ischemic burden such as PET or FFRCT should be considered upfront rather than myocardial perfusion imaging when available.

Tricuspid Valve Therapies

Tricuspid regurgitation (TR) has generally been ignored in the therapeutic algorithm of patients with heart disease. There are several reasons for that.

Perhaps the most common reason is that almost 90 percent of patients with severe tricuspid regurgitation (TR) have left-sided heart disease such as mitral valve disease or left ventricular systolic dysfunction. In these instances the TR is thought to be a bi-product of the left-sided disease and most therapies are directed at addressing the left-sided disease.

There is also no effective therapy in the treatment of tricuspid regurgitation. As a matter of fact the most prescribed treatment for this disease is a diuretic. This is in part because surgical literature has shown that patients with primary TR who undergo surgical repair/replacement have higher mortality as well as morbidity compared to other valvular therapies. As a result cardiologists are reluctant to recommend corrective surgery in patients with secondary TR unless the patient was undergoing surgery for another cardiac condition at the same time.

However, there has been a paradigm shift over the past few year in our approach to the treatment of severe TR. A major part of this shift is due to the proliferation of transcatheter techniques in the treatment of other valvular heart diseases such as mitral and aortic valve.

It is observed that patients do worse after transcatheter aortic replacement or transcatheter mitral repair if they have concomitant tricuspid regurgitation. This is in line with the data from the surgical literature. As a result, there is an explosion in device development for percutaneous treatment of tricuspid regurgitation to be done either alone or in conjunction with percutaneous treatment of other valvular heart diseases. Many feasibility trials are currently looking at safety of these devices and a few trials are either ongoing or starting to look at their efficacy.

MitraClip developed to treat mitral regurgitation remains also the most prevalent device used to treat TR in the worldwide registry.

 

 

 

 

 

 

 

 

 

 

 

 

 

Nevertheless, the road ahead from diagnosis to treatment of TR is certainly torturous and long and perhaps it will take many years for us to have a clear understanding of when and how to treat this disease entity.

For one, the timing of intervention to give the patient the best prognosis is poorly understood. In most surgical trials, patients had advanced disease at the time of the operation. It is postulated that intervention should be done earlier in the disease course to give patients the best prognosis. However, the exact timing for transcatheter intervention remains a point of discussion.

Currently surgical correction is considered in patients based on the annular diameter of the tricuspid valve. This might not be the best surrogate marker to assess the severity of tricuspid regurgitation effect on the right ventricle. Many other parameters are being investigated to determine the deleterious effects of TR on the right ventricule. Echocardiographic measurements such as right ventricular strain are among such parameters.

Longitudinal follow up of these parameters will make it more clear as to when to intervene in the disease process to obtain the best prognosis.

The other obstacle in the treatment of TR is the tricuspid valveā€™s anatomy. It is comprised of three unequal very thin leaflets, the anterior leaflet the longest and posterior leaflet the shortest. Its location and thin nature of the leaflets make echocardiographic imaging especially difficult during any transcatheter procedure.

Optimal intraprocedural imaging is essential in successfully treating the valve. The development of intracardiac imaging as part of the percutaneous devices currently being developed should alleviate some of this difficulty.

Finally, the proximity of other cardiac structure to the tricuspid valve should be taken into account while planning for transcatheter intervention. The right coronary artery is positioned to the lateral aspect of the valve and conduction system to the septal portion. Therefore, the risk of right coronary perforation or inducing conduction disturbance during the procedure should be taken into account. Obtaining a cardiac CT and meticulously evaluating the tricuspid valve and its relationship to other cardiac structures is of paramount importance prior to most percutaneous therapies.

Anatomy of the tricuspid valve and its relationship to other cardiac structures.

 

 

 

 

 

 

 

 

 

Tricuspid valve pathology is perhaps the last valvular pathology to be addressed by transcatheter techniques. There are a lot of challenges ahead as outlined above. Perhaps that is why tricuspid intervention is one of the more exciting fields to be involved in at this time. Also, its treatment could be the most rewarding for the patients as well as physicians.

Watch our recent video presentation on Tricuspid Regurgitation.