TTHealthWatch is a weekly podcast from Texas Tech. In it, Elizabeth Tracey, director of electronic media for Johns Hopkins Medicine in Baltimore, and Rick Lange, MD, president of the Texas Tech University Health Sciences Center in El Paso, look at the top medical stories of the week.
This week’s topics include early ablation for atrial fibrillation, treating heart attacks promptly, triglyceride lowering and cardiovascular outcomes, and making defibrillation more effective.
0:51 Heart attack treatment times
1:51 Only 17% of the time by guidelines
2:51 Each hospital must evaluate
3:50 Thrombolytic therapy
5:01 67% with previous CVD
6:04 Higher incidence of adverse renal events
6:23 Refractory defibrillation
7:23 Double defibrillation had higher survival
8:23 Just experience
8:30 Early treatment of atrial fibrillation
9:30 Much less recurrent fibrillation
10:30 Remodels atrial tissue
11:30 Both done safely in experienced centers
Elizabeth: Does lowering triglycerides help reduce cardiovascular disease risk?
Rick: Rapid treatment of acute heart attacks.
Elizabeth: Does early treatment of atrial fibrillation help stave off furthering of the condition?
Rick: And making defibrillation more effective for people that have had a cardiac arrest.
Elizabeth: That’s what we’re talking about this week on TTHealthWatch, your weekly look at the medical headlines from Texas Tech University Health Sciences Center in El Paso. I’m Elizabeth Tracey, a Baltimore-based medical journalist.
Rick: And I’m Rick Lange, president of Texas Tech University Health Sciences Center in El Paso, where I’m also dean of the Paul L. Foster School of Medicine.
Elizabeth: Rick, of course, this is the AHA (American Heart Association) meeting week and that’s why everything this week is from the heart. Since you’re a heart man, I’m going to let you kick it off.
Rick: Well, Elizabeth, let’s talk about one of the most frequent heart conditions, heart attacks, when there is a blood clot in one of the arteries that prevents blood flow to the heart and that can result in immediate irregular heart rhythms, in which case people need to be defibrillated. Or if they survive without a rhythm abnormality, there is part of the heart muscle that dies. We have the saying called, “Time is muscle.” What you want to do is you want to open that artery up as quickly as possible to preserve the heart muscle.
This was a study that looked at two different time periods — in 2018 and 2021 — of almost 115,000 patients that received heart attack treatment at over 648 hospitals called Get With The Guidelines – Coronary Artery Disease (GWTG-CAD) Registry. They wanted to ask, “How well are we doing, and does getting the heart attack treatment earlier actually affect mortality?”
There are several different goals. We want to make sure that the first medical contact when they get their artery open is less than 90 minutes. In people that present to a hospital that doesn’t have a cardiac cath lab, that only happens about 17% of the time. In those individuals that have the artery open early, it reduces mortality of about 50%. Anything and anywhere that delays less than the guidelines recommend essentially doubles mortality. That’s what this study showed.
Elizabeth: This study is published in JAMA. I would like to hear your thoughts on what accounts for these delays and would it be helpful to engage EMS, for example, in making sure that they always transport to hospitals that have a cath lab.
Rick: It’s different for different localities. One of the things that the authors recommend is for each of the individual hospitals to identify where your delay is and address that. You want to have the EMS people trained so they recognize a heart attack in the field. They can call ahead to the hospital and they can already initiate activating the cardiac cath labs.
The second, as you said, is making sure that individuals get to a cardiac cath lab or regional center as quickly as possible. For those that just walk into the hospital, for them to be seen very quickly to get an EKG done, so we can establish whether it was a heart attack and then activate the cardiac cath lab is also important. There are a number of different factors, and it is local. That’s why these need to be evaluated at the hospital level.
Elizabeth: You say that each hospital needs to take a look at where their delays are occurring in their particular facility. I’m wondering how complicated it is to follow somebody as they come to your ED and then go through the whole evaluation and treatment.
Rick: It’s really not very difficult. Most hospitals should set up committees to do that. For example, you know that you want the individual from the time they present to the emergency department to have an EKG done in less than 10 minutes. Each of these can be segmented and evaluated.
Elizabeth: One question I have, of course, is that we’ve been seeing an awful lot about “maternity care deserts” in different parts of the country. Let’s talk about the distribution of cardiac cath labs.
Rick: You’d like for — when a person comes to a hospital that doesn’t have a cardiac cath lab — is to get them out within 30 minutes. It’s obviously more difficult in very rural areas. In those settings, the patient oftentimes get thrombolytic therapy that should dissolve the clot. It’s not quite as effective as a balloon, but it’s still much more effective than not treating the patient and then moving the patient.
Elizabeth: Let’s turn to the New England Journal of Medicine, where we will spend the remainder of our time this week, taking a look at prevention of heart attacks. We know that a lot of things are involved in somebody’s heart attack risk. One thing is high triglyceride levels. It’s unclear, however, whether reducing these levels will reduce the incidence of cardiovascular events. This agent called pemafibrate was tested in this study to reduce triglyceride levels and also associated with improvements of other lipids. The question is, does this really help?
This was a study that enrolled patients with type 2 diabetes, mild to moderate hypertriglyceridemia, and that was a triglyceride level 200 to 499 — which to me doesn’t sound moderate, but maybe you’re going to disabuse me of that notion — mg per dl, and low high-density cholesterol levels.
They were given pemafibrate twice daily, or a matching placebo. They had almost 10,500 patients, 67% of whom had had previous cardiovascular disease. They followed them up for 3.4 years. They did see that the pemafibrate was able to achieve a reduction of 26%+ for triglycerides, 26% for VLDL, and almost 26% for remnant cholesterol. The bad news is, it really wasn’t very helpful with regard to these other outcomes that they were looking for, in spite of the fact that they did see improvements in this profile.
Rick: This is one of different agents that have been very effective in lowering triglycerides in people that have high triglycerides, yet it hasn’t reduced the risk of heart attack, stroke, or cardiovascular death.
This is very different than the story with cholesterol, and lowering cholesterol, especially the LDL, has been beneficial. In this particular study, they targeted a specific population they thought it might be helpful: diabetics, high triglycerides, and low HDL. This was a group that, gosh, they thought if anything was going to work this would be the group. Again, lowering triglycerides really didn’t improve cardiovascular outcomes.
Elizabeth: Yes. It seems like it’s got to be a surrogate for something else that’s going on. Also, they had a higher incidence of adverse renal events and VTE.
Rick: Relatively minor. Then when they went and looked at it, it really wasn’t that big. One of the things that was interesting, though, is this may have some beneficial effects with regard to liver. They may turn their attention from using this for cardiovascular disease to actually liver disease or fatty liver.
Elizabeth: Let’s turn to your next one, as I said, also in NEJM.
Rick: I mentioned the fact that when people have a heart attack, one of the complications is an irregular heart rhythm, or what’s called ventricular tachycardia or ventricular fibrillation. Oftentimes, that’s what causes death in people that have an out-of-hospital cardiac arrest. There are some people that are just refractory to defibrillation in the typical method.
What these investigators did was say, gosh, can we change the defibrillation method a little bit and make it more effective in people that have refractory heart rhythm? The two ways that you can do it is usually the paddles are placed on the front part of the chest. What if you put one on the front and one on the back? The second is to use two defibrillators, one where the paddles are placed on the front and another where it’s placed on the front and back, and then you sequentially defibrillate the patient.
In this particular study, they tried 3 different techniques, moving the paddles, doing double defibrillation, and then just trying to repeat standard fibrillation. What they found out was when they used the double defibrillation, it had higher survival than the standard, 30% versus 13%. When they just changed the paddles on the front and the back, it also was associated with a higher survival, 22% versus 13%. That’s great news in terms of making refractory defibrillation more successful.
Elizabeth: I’m going to ask you to recall, lo these many years ago, a notion that CPR ought to be delivered dorsally versus ventrally. Talk to me about why this might work.
Rick: When you think about where the heart is located, where the left ventricle is, a lot of it’s on the back side, the posterior part of the heart. When you place the paddles just on the chest wall, you don’t get as much electrical activity.
Elizabeth: In your abundant experience clinically, what are the challenges that would be faced in employing these techniques?
Rick: The one where you’re just switching the defibrillation pads from the front to the front and back called a vector change defibrillation. That’s really very easy to do. The other one where you do double sequential external defibrillation actually is a little bit more difficult because you have to have two defibrillators. But, again, a lot of that is just experience.
Elizabeth: Now, finally let’s turn to the treatment of atrial fibrillation. We’re, of course, aware that many people develop atrial fibrillation as they age, but there is a whole population of folks who have it at all different ages.
In this case, they were taking a look at, “Gosh, if we use cryoablation to try to deal with where these aberrant electrical impulses arise early on in the development of this condition, can we improve outcomes and also is this superior to medical therapy for these folks?”
This is a 3-year follow-up of patients with paroxysmal untreated atrial fibrillation. They had been randomly assigned to undergo either initial rhythm control therapy with cryoballoon ablation or to receive antiarrhythmic drug therapy.
They had a total of 303 patients, 154 assigned to the rhythm control therapy with the cryoballoon and 149 in the drug therapy group. Only 3 patients, or 1.9%, in the ablation group had an episode of persistent atrial fibrillation as compared with 7.4% in the med group. Recurrent atrial tachyarrhythmia in the ablation group, almost 57% of those folks did experience that, compared to almost 78% of the group who were treated with medicines. In the ablation group, 5.2% and in the anti-arrhythmic drug group almost 17% had been hospitalized.
It sure looks like treating this paroxysmal atrial fibrillation with the cryoballoon ablation, but maybe with other techniques also, was associated with a lower incidence of persistent fibrillation, recurrence of this arrhythmia, or hospitalization.
Rick: You mentioned something and I just want to drive the point home to our listeners. If someone has paroxysmal atrial fibrillation, that means it occurs intermittently. It appears that over the course of time paroxysmal atrial fibrillation makes the left atrial tissue remodel so that it’s more predisposed to developing persistent. Starting the ablation early before the tissue has begun to remodel, I think that’s an important message.
Elizabeth: It’s still rather disappointing that 57% in the ablation group did develop an arrhythmia again.
Rick: I’m not terribly surprised at that, Elizabeth, any atrial arrhythmia. It doesn’t talk about whether it’s long or short. It doesn’t show what kind it is. But these are individuals that are already predisposed to it, and what you’re trying to do is prevent persistent atrial fibrillation.
Elizabeth: I guess I would ask you to also comment on, it’s not just cryoablation. I mean, ablation can be undertaken with other techniques.
Rick: Right. Radiofrequency ablation or a little bit of heat, or a little bit of cryo. I’m not sure that there is a huge difference between the two. It’s really what the centers are most comfortable with, and it relates more to the complication rate. There are different types of complications, or fewer complications with cryoablation, than are with radiofrequency ablation. But both can be done safely in experienced centers.
Elizabeth: I would also finally ask you to comment on, is there any role in these people who have had ablation with going on meds anyway?
Rick: Oftentimes, these people are on medications either to control the rate, that is, if they have recurrent atrial arrhythmias to try to keep it slow, or antiarrhythmic medications. It’s a combination of the ablation and the medication. Now, ideally you’d like to get them off medication, but sometimes people need to be on it as well, so the ablation may modify the risk but not completely take it away.
Elizabeth: I guess we need to close the loop here and just remind folks that the dangers of atrial fibrillation over the long haul are…
Rick: Well, if they are untreated, specifically if they don’t take anticoagulation, it’s primarily a stroke or a clot forming. That clot can go to the venous system or it can go to the arterial system. When it goes to the arterial system in the brain, it causes a stroke and it raises the risk of stroke about 5- to 10-fold. That’s why it’s important to recognize it and to treat it appropriately either with medications we have described, cryoablation, or, more importantly, making sure they are on anticoagulation.
Elizabeth: On that note then, that’s a look at this week’s medical headlines from Texas Tech. I’m Elizabeth Tracey.
Rick: And I’m Rick Lange. Y’all listen up and make healthy choices.