STEMI Interventions: The Finest Indication for PCI

Author(s): 

Cath Lab Digest talks with Sameer Mehta, MD, FACC, about his upcoming LUMEN meeting, the second edition of the Textbook of STEMI Interventions, and the SINCERE database.

Can you tell us about the February 2011 LUMEN meeting, focusing on the process and the procedure of ST- elevation myocardial infarction (STEMI) interventions?

This is the 10th year for LUMEN, now converted for the third year in a row into a pure STEMI meeting. I believe it is the largest subject-centric acute myocardial infarction meeting in the world. LUMEN will be held February 24-26, at the Marriott Marquis hotel in Miami. The faculty will contain many world experts, experts both in the STEMI procedure and in the STEMI process. I am also very pleased to announce that Dr. Alice Jacobs, chairperson for the American Heart Association’s Mission: Lifeline, will be the recipient of the LUMEN achievement award in 2011.

There are several new topics. First, LUMEN will place a strong emphasis on transradial interventions. I have been struck by the increasing international rates of STEMI interventions done via the radial artery. The U.S. is lagging behind, and LUMEN will make a very sincere and determined effort to narrow this gap.

Towards that end, I have brought in some of the world’s experts in transradial interventions, including Dr. Tejas Patel, who has, over the last decade, been running the TRICO (Transradial Intervention Course) in Ahmedabad, India. Dr. Patel has trained thousands of cardiologists in the use of radial access.

Co-chairing at LUMEN with Dr. Patel will be Dr. Sunil Rao from Duke University Medical Center, a well-known authority in this field. LUMEN attendees will also benefit from the expertise of Miami-based transradial expert Dr. Ramon Quesada. The faculty will be conducting workshops, discussing tips and tricks, and providing practical lessons on radial access in STEMI interventions. Left ventricular assist devices will continue as an area of strong focus. LUMEN will also offer a look at cell therapy for STEMI interventions, with talks by Dr. Timothy Henry of Minnesota Heart, as well as Dr. Ajit Mullasari from the Madras Medical Mission, in Chennai, India, one of the most expert institutions in this area internationally. Door-to-balloon (D2B) management continues as an important focus for 2011. It will be discussed via an interactive, town hall-style meeting, conducted on the first day, with all the LUMEN co-directors. Speakers will review specific examples of STEMI interventions, pinpointing challenging areas and offering strategies for improvement.

Specific components of the STEMI procedure, particularly the management of thrombus, will be discussed. Finally, there are 8 workshops specifically tailored to the needs of the interventional cardiologist, the clinical cardiologist, the cardiac surgeon, the nurse, the cardiovascular technologist, as well as various administrators who may also benefit from attending LUMEN.

The latest Textbook of STEMI Interventions launched in November. What are some of the highlights from this second edition of the textbook?

The Textbook of STEMI Interventions discusses both the process and the procedure of STEMI interventions. It is a 650-page follow-up on the first volume. Collected within the book are 100 illustrated examples, divided into five sections: basic skills, complex interventions, thromboaspiration, rheolytic thrombectomy, and cardiogenic shock. These 100 illustrated examples provide a very large compendium of what any one operator can expect. A STEMI intervention is like a blind date. You cannot anticipate what you are going to confront, whether it is going to be significant tortuousity, the hurdles of traffic, or a dense, organized thrombus. The textbook provides a very detailed look at thrombus management. There are chapters dedicated to clinical trials, to updated American College of Cardiology/ American Heart Association-focused guidelines, improving EKG skills, pharmacology, and strategically improving D2B times. A very large section discusses what is happening internationally with STEMI interventions, presented by experts from Canada and Singapore. We hear from Dr. Antonio Colombo, who writes from the perspective of STEMI interventions in Europe, and there are details about emerging countries such as India. A substantial portion is devoted to left ventricular assist devices: one chapter addresses the pathophysiology, and another presents tips and tricks about how to benefit most from the use of left ventricular assist devices in STEMI interventions. Among many excellent authors, I am delighted to have a chapter by Dr. Derek Yellon discussing reperfusion strategies. The second edition is also a wonderful update on pharmacology, offering a chapter on IIb/IIIa inhibitors by Dr. Dean Kereiakes, a general review chapter by Dr. Raghotham Patlola and Dr. Craig Walker, a discussion of the broader aspects of pharmacology by Dr. James Ferguson, and finally, a detailed chapter on prasugrel by Dr. Mike Gibson.

The second volume of the textbook holds everything that an interventional cardiologist needs to know about STEMI interventions. The book is now available for shipping. It can be ordered through http:// www.stemiinterventions.com, and also be purchased directly at LUMEN and the upcoming American College of Cardiology meeting.

The textbook, in part, arose from the intense experience of the SINCERE database. How is the database progressing?

The Single Individual Community Experience Registry for Primary PCI (SINCERE) database is currently at 690 SHORT D2B STEMI interventions (total patients approx. 1,000, including about 30% false alarm rates) patients over almost seven years, all short D2B time interventions. The database was initially begun at 6 hospitals, now down to three, because these three hospitals have kept me extremely busy.

It was probably in the first 100-200 cases that the “10 commandments” for doing STEMI interventions were formulated (Table 1), and all 10 commandments stay true to this day. Within a specific commandment, there have been some changes, most notably that I am using much larger doses of intracoronary nitroprusside. An intracoronary vasodilator is necessary to augment the distal microvasculature flow. Numerous agents can be used for this purpose — verapamil, diltiazem, nicardipine and nitroprusside — my favorite is intracoronary nitroprusside. It does produce some hypotension, which is easily taken care of by giving bolus doses of intracoronary neosynephrine. The benefits of using an intracoronary vasodilator include a dramatic and significant increase the myocardial perfusion grade.

Intracoronary nitroprusside typically will increase perfusion grade by 1. I am now following my constructed technique in the following manner to achieve the best results with nitroprusside. I first ascertain that the PCI results and stent placement are adequate. Then I remove the guide wire (which is itself acting as a nidus of thrombus). I will then start with boluses of 50 to 100 mcg of nitroprusside, and frequently go on to use larger doses, up to even 600 and 800 mcg! Yes, this may seem alarming, and it did not come easy for me to comprehend, let alone practice. This, in turn, is the advantage of a very large, not conflicted database. In the first 200 cases in the SINCERE database, the mean dose of nitroprusside was 50 mcg, and I used it in about 30-40% of procedures. However, as my confidence grew from observing the stupendous results from this maneuver, my use of nitroprusside has significantly increased with both the frequency of use (91% presently) and in using larger doses. I have moved significantly away from the use of nitroglycerin. Nitroglycerin is more of an endothelial, nitric oxide-mediated drug. There is not much of a role of endothelium-mediated derivatives, as the problem is the presence of thrombus, which is a pathophysiological mechanism of STEMI. Both nitroglycerin and nitroprusside cause hypotension. I therefore prefer the benefit from increased distal microvasculature flow with nitroprusside, than to cause hypotension with nitroglycerin.

I continue to modify my use of bare metal versus drug-eluting stents. Recently, there have been stronger data for the use of drug-eluting stents for STEMI, although the follow up from the DEDICATION trial was somewhat tempered in its enthusiasm.1 So I think this chapter is still open, although there appears to be a larger role for drug-eluting stents. My use of drug-eluting stents in STEMI is for four indications: left anterior descending coronary artery (LAD) lesions, small vessels, long lesions, and in-stent restenosis. Beyond that, I think a lot of patients do fine with bare metal stents. We have a burgeoning population of patients with no insurance; for these patients, the cost of antiplatelet agents can be quite high, and for these patients, bare metal stents are more appealing.

I am converting more of my patients into prasugrel, because that appears to be a better drug for STEMI. The onset is quicker; you don’t have to be burdened down with clopidogrel non-responders. We use it as a bolus of 60 mg in the ER and use it for most patients, except for the elderly, those with a history of cerebrovascular accidents and those with low body weight.

I use bivalirudin on almost 100% of patients. Many trials have demonstrated it as a superior anti-thrombotic agent and it significantly reduces bleeding, which is known to be an independent predictor of mortality. I use it as a bolus and a drip; the latter is continued for up to 4 hours post procedure. It appears that the benefits of bivalirudin will get accentuated with use of transradial STEMI procedures. It also appears that any lingering doubts about stent thrombosis with bivalirudin will be completely abolished with the use of prasugrel. There has been no incidence of stent thrombus in the SINCERE database that resulted from the use of bivalirudin, although there have been three such cases that can be attributed to inadequate thrombus retrieval. Glycoprotein IIb/IIIa receptor inhibitors have been used in about 35% of SINCERE cases, always in the following situations: 1) when there is a high thrombus burden; 2) when there is residual thrombus; 3) in presence of side-branch involvement, and 4) where the angiographic result is not perfect.

In this latter situation, when there is a lack of myocardial perfusion grade (MPG) 3, continuing chest pain or residual ST elevation, I feel that a 12-hour drip of abciximab is very useful. I have also continued to use most IIb/IIIa inhibitors via direct intracoronary delivery. The Clearway catheter (Atrium Medical Corp., Hudson, New Hampshire) is the most sophisticated and probably the best way of delivering intracoronary abciximab. The true advantage of delivering intracoronary abciximab is that it achieves very high concentrations, almost 500x more than the intravenous route. At this stage, when intracoronary abciximab is locally delivered, it acts more as a de-thrombotic agent rather than as a IIb/IIIa agent.

To measure STEMI success, I have always used the following four parameters: ST segment resolution, relief of chest pain, TIMI grade 3 flow and MPG 3.

Recently, the Mehta classification for selective management of thrombus in STEMI lesions has been published (Table 2).2 I strongly feel that a single strategy for thrombus management will be generally ineffective, be that the use of aspiration or mechanical thrombectomy or the use of catheters for local drug delivery. This is primarily because thrombus is labile and it varies between a soft, red, friable but easy to debulk fresh thrombus in early presenters to dense, organized thrombus in late presenters. I have therefore meticulously worked with a compulsive management of thrombus based on thrombus grade. In most cases, for low-grade thrombus (grades 1-2), direct stenting is appropriate. For anything in the moderate grade (grades 2, 3, and possibly 4), a strategy of using aspiration thrombectomy is superior. Although several catheters are available, in my experience, the Export catheter (Medtronic, Inc., Minneapolis, Minn.) is the best. Finally, for lesions with high-grade thrombus, there has to be the presence of a mechanical device such as the AngioJet (Medrad, Inc., Warrendale, Pa.) There are going to be cases that will have large thrombus burden, and this classically occurs in patients with late presentation, who have dense, organized thrombus. Unless you have a mechanical device able to remove this dense, organized thrombus, the results will not be satisfactory.

Beyond this strategy to diligently manage thrombus, I use aspiration thrombectomy as my default level-one strategy, based on the following reasons: 1) aspiration catheters are no more time-consuming or difficult to use than a simple balloon catheter; 2) they are monorail devices; 3) they are relatively less expensive; 4) have a class II indication for the management of thrombus in STEMI. Certainly, aspiration catheters do not track as well as one would like to believe. Furthermore, they kink easily and they are not as supportive in terms of mechanical strength. But, based on the reasons given, I will almost invariably use an aspiration catheter, and then follow it up with stenting. I have almost completely moved away from the use of balloon catheters, using them only in extremely rare conditions: 1) in cases where there is overwhelming ischemia, and I want to quickly obtain some antegrade flow before using an aspiration catheter; 2) a situation where I am not sure whether the guidewire is in the true lumen. A quick inflation at low atmospheres with a 2.0 mm balloon catheter, for example, will easily confirm that the guide wire is in the true lumen; 3) And finally, what I call the 88-minute use of a balloon catheter.

Often you are handed a patient with the clock clicking to its 90-minute conclusion and a quick balloon inflation cheats to fulfill the grand achievement of a D2B time! But beyond these reasons, use of a balloon catheter will only increase distal embolization.

What about D2B times?

In the first 2 to 3 years of experience with the SINCERE database, it was a major assignment trying to achieve D2B times. At that time, we were constantly struggling to perform the procedure in 90 minutes. It is now quite easy to achieve D2B times in less than 90 minutes; in fact, some hospitals have even become so good that they are aiming to achieve D2B times of less than 60 minutes. The entire integrative approach to coordinate systems of care has become so much more efficient that the last time we missed a D2B time was 150 cases ago! During the entire year of 2010, there has not been a single patient that has gone beyond the D2B time of 90 minutes. However, there is an important caveat here: the SINCERE database does not include transfer patients. As delighted I am about achieving D2B quite easily and very predictably, the transfer patient is an entirely different challenge. So far as a transfer patient is concerned, I regretfully accept that we have not done very many transfer patient with D2B times of 3 and to other, similar trials for managing such patients. If we are not able to efficiently transfer these patients, they should not be denied early (door-to-needle time

The other problem with the entire STEMI pathway is the false alarm rates. Hospitals are extremely skillful at achieving and monitoring D2B times. Achieving this metric means increased incentives and funding from CMS, as well as helpful with Joint Commission measurements. What institutions are not measuring, as they should, and which is a very large and important segment, is the false alarm rate. The false alarm rate is the rate at which the cardiac cath lab has been activated and there is no demonstrable culprit lesion. I am not talking about the presence of coronary artery disease, but there has to be a clear “culprit lesion” that correlates with the EKG changes. As an example, an ST elevation in the inferior leads should demonstrate a culprit lesion in the right coronary artery or in a dominant left circumflex. The false alarm rate, as determined by the American College of Cardiology and the American Heart Association standards, should be no higher than 15%. I suspect that the false alarm rate is higher than 15% for several institutions in the country. It is definitely higher at the hospitals at which I work. The false alarm rate needs to be followed as rigorously as D2B time. The 2nd edition of the Textbook of STEMI Interventions provides a detailed discussion on the overexuberance in following only D2B times. The D2B times then become a loadstone in achieving excellent STEMI care, as they are subject to manipulation, and that they may simply be a wrong metric to follow.

Where do you see system challenges?

There are several weak points in the STEMI pathway that can be addressed, starting with the EMS. If an EMS truck has 100% transmission capability, most issues with false alarm rates originating at this point can be eliminated. Yet, in the entire United States, less than 25% of EMS trucks have this capability, and within Miami, that rate is also 25% or less. In certain parts of the country, like California, the ability to transmit the EKG is higher (50-60%), which is how it should be. In Denmark, almost all ambulances have EKG transmission capability. Lack of transmission capability means the EKG interpretation is solely performed by the EMT and the quality of the results therefore depends on their level of training. There is an immense amount of variability in the systems. The RACE program in North Carolina, the Ottawa system in Canada, and the EMS systems in the Minneapolis area and Los Angeles contain some of the best-trained EMTs. In Ottawa, it has been found that there is a 95% concordance between EKG interpretation by a cardiologist and the EMT. So you can see, we have much to catch up with Canada and Europe in areas of pre-hospital care and in the management of the transfer patient. It is unfortunate that we are still having such a high false alarm rate, because with training, these flaws can be greatly reduced. There are 5 or 6 major diagnoses: bundle branch block, left ventricular hypertrophy, the left anterior fascicular block, pericarditis, left ventricular hypertrophy with strain, and a few other smaller, less common presentations which one should be able to rule out with good training for interpreting the EKG. It is why, during LUMEN, a dedicated EKG certification course remains part of the meeting.

You mentioned the growth of transradial procedures internationally. Are there any other global, STEMI-related trends?

This year, the Great Minds symposium was held in February in Singapore. The chairperson was Dr. Ian Meredith, who brought to our attention that while there is a 10-15% decline in the U.S. in PCI, there is a 20-30% increase across the board in most nations in the Asia-Pacific region! It is possible that China and India, within the next few decades, will equal the rates of PCI being performed in the U.S. Numerous cities in India are working to develop population-based STEMI programs. There are programs that are very sophisticated, with a large penetration of good ambulance structure, and areas that are first concentrating in urgently delivering thrombolytic pathway. There is very broad, heterogenous spectrum of STEMI care that is delivered in poorer and less developed countries, but there is no doubt in my mind that providing urgent STEMI care will reduce the mortality from AMI in various countries, particularly in the Asia-Pacific region.

I also want to mention a study with which I am involved, the PRINCE study (Puerto RIco Nationwide Collaborative Experience). PRINCE is a longitudinal, population-based, STEMI program that is coordinating systems of care for treating AMI in Puerto Rico.

Any final thoughts?

I feel gratified and humbled to practice an amazing procedure, and stupefied watching its powerful results. STEMI interventions are easily the finest indication for PCI, and the procedure is often life-saving and dramatic in its healing. I am often the recipient of great love and gratitude from the patients and from their loved ones. To be trusted with someone’s heart is a privilege that I have never taken for granted. In the process of performing these amazing procedures, the robust SINCERE database has been created and it now serves as a fabulous source for research and publications. It has also provided a foundation for writing two textbooks in STEMI interventions. Inadvertently, I may have also created a new specialty of a STEMI interventionalist. I sincerely hope that my work will inspire similar commitment and that the lessons that I have learnt from SINCERE will be found useful by other cardiologists. I feel very satisfied that D2B times are coming down. We need to remain vigilant, however, and monitor the true impact of D2B times, eventually searching for a better indicator of the true ischemic period. We must recognize that the D2B time is simply a last in a series of events that herald an acute MI, and that efforts have to be galvanized in urgently moving a patient into the STEMI pathway. Finally, I maintain that the D2B time is simply the low-hanging fruit in STEMI interventions and that the greater challenges involve legislation and patient education.

I encourage readers to attend LUMEN and hope that the newly released second edition of the Textbook of STEMI Interventions will also provide very useful information.

References

1. Kaltoft A, Kelbaek H, Thuesen L, et al. Long-term outcome after drug-eluting versus bare-metal stent implantation in patients with ST-segment elevation myocardial infarction: 3-year follow-up of the randomized DEDICATION (Drug Elution and Distal Protection in Acute Myocardial Infarction) Trial. J Am Coll Cardiol 2010 Aug 17;56(8):641–645.

2. Mehta S, Alfonso CE, Oliveros E, et al. Adjunct Therapy in STEMI Intervention. Cardiology Clinics 2010; 28(1): 107–125.

3. Cantor WJ, Fitchett D, Borgundvaag B, et al. Routine early angioplasty after fibrinolysis for acute myocardial infarction. N Engl J Med 2009 Jun 25;360(26):2705–2718.

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Dr. Sameer Mehta can be contacted at mehtas@bellsouth.net

More information about LUMEN, held February 24-26, 2011, in Miami, Florida, is available at www.lumenami.com.

More information about the Textbook of STEMI Interventions is available at www.stemiinterventions.com

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