Today’s vlog is on the subject of heart failure and in particular on a special type of pacemaker which can make a significant improvement to the quality of life and length of life in patients with heart failure.
What is heart failure?
The heart is a pump and if the heart is in some way damaged – be that by a heart attack or a virus or harmful drugs then the heart is unable to pump out enough blood to meet the body’s requirements especially when the body is asking for more blood such as during exercise. This inadequacy of the heart is often manifested with symptoms of breathlessness, fatigue and exercise intolerance and this is termed heart failure. Virtually all forms of heart disease, if progressive and if left unchecked will eventually end up with the heart weakening and thereby developing heart failure
People with heart failure in general will not live as long as they would have if they had a strong heart and in general they do not feel as good as they would if they had a strong heart and therefore heart failure will negatively impact on both length of life and quality of life.
It is also important to understand that heart failure if left untreated is a progressive condition and I will try and explain how this happens.
When the heart pumps less blood out, our kidneys receive less blood than they expect and they therefore act almost in the same way as when one is dehydrated. They start retaining more salt and water in order to boost the circulatory volume. However the problem is not that we are lacking volume, it is just that the volume is not getting to the kidneys and therefore by increasing the volume, the kidneys still don’t get the blood they expect and therefore they continue to increase retention of salt and water and slowly and gradually the amount of volume in the vascular system and the amount of blood entering the heart progressively increases and the heart which has to contain all this blood starts stretching and in doing so, it becomes flabbier and weaker.
The aims therefore in the management of heart failure are to try and firstly improve the patients quality of life by relieving symptoms but also try and prolong their life by giving them medications that reduce the progression of heart failure. We now do have some really good medications that help do both and these include:
MRAs – Mineraloreceptor antagonists
And ideally anyone with heart failure should be on all these medications unless they are intolerant or in some way the medications are contraindicated.
Nevertheless despite all the medications, a substantial proportion of heart failure patients remain significantly symptomatic and this is where cardiac resynchronization therapy has proved to be a game changer.
What we have realized is that as the heart gets weaker, it also gets bigger and flabbier and therefore electrical impulses take longer to get to some parts of the heart (usually the free wall of the left ventricle) compared to others. This means that some walls of the heart end up contracting earlier than others and this is referred to as cardiac desynchrony.
The way to think of cardiac dyssynchrony is to think of a sack of potatoes. If you want to empty a sac of potatoes most efficiently, you would want to hold the bottom of the sac at both ends and then tip it over. If you only held one corner then some potato would fall to the other side rather than fall out of the sac. This is very similar to what happens with blood when it comes out of the heart. The heart will function more effectively if all the walls contract in synchrony and the greater the cardiac dyssynchrony the more inefficient the heart is.
How do we know if there is cardiac dyssynchrony?
The easiest way is to look at the ECG. On the ECG, we have the QRS complex and the duration of the QRS complex guides us on how long it has taken for the electrical impulses to go around the ventricles. The longer the QRS duration, the more the dyssynchrony esp if there is a pattern called Left bundle branch block. The usual duration of the QRS is less than 120ms and if the QRS is more than 120ms then there is some dyssynchrony and if it is more than 150ms then there is a lot of dyssynchrony. In advanced heart failure, we also know that the longer the QRS, the poorer the prognosis and therefore scientists became very interested in exploring ways to reduce this dyssynchrony. This led to the development of a special type of pacemaker called a BiV pacemaker which involved putting a lead in the right ventricle and one in a vessel called the coronary sinus which overlies the left ventricle. This then allows a pacemaker to deliver electrical impulses to the ventricles in synchrony and hence allow for a more effective contraction of the heart.
In 2002, a study called MIRACLE was published in the NEJM in which 453 patients with moderate to severe heart failure with an ejection fraction of less than 35% and a QRS of greater than 130ms were studied. 228 patients were randomized to receive the BiV pacemaker (in addition to conventional therapies) and 225 patients were just given conventional therapies and no BiV pacemaker. The results showed that patients who received the BiV pacemaker had a more marked improvement in their functional capacity, an improvement in their walking distance, as well as an improvement in the ejection fraction. In addition, the group with the BiV pacemaker were less likely to be hospitalized for heart failure flare-ups.
So on the basis of these data there was little doubt that BiV pacing could be a useful adjunct to improving quality of life in patients with significant heart failure and ECG evidence of dyssynchrony – but could it also improve prognosis – i.e length of life?
This was looked at by a study called COMPANION which was published in 2004. In this study the investigators took 1520 patients with advanced heart failure and a QRS duration of >120ms and randomized them to one of 3 groups.
The first group were just asked to take their usual medications. The second group were given a biventricular pacemaker. The third group were given a biventricular pacemaker which was combined in the same device with a defibrillator and they found that the risk of the combined endpoint of death from hospitalization for heart failure was reduced by 34% in the pacemaker group and 40% in the pacemaker defibrillator group compared to the medications group.
There was another study called CARE-HF study which looked at 813 patients and found that in patients with heart failure and cardiac dyssynchrony, cardiac resynchronization improves symptoms and quality of life and reduced complications and the risk of death and on the basis of all these data, all patients with significant heart failure who have evidence of dyssynchrony on their ECG should be considered for a BiVentricular device if they are symptomatic despite medical therapy.
There are some other important things to note.
Only 7/10 patients who receive a Biventricular device feel the benefits of it. Scientists are still trying hard to see whether there are ways by which we can be sophisticated about identifying who respond to the BiV pacemaker and who wont before they put in the pacemaker
Patients in whom the cause of the heart failure is a previous heart attack seem to benefit more than patients in whom the heart failure has been caused by some other etiology like a virus or familial cardiomyopathy
It is patients with a left bundle branch block pattern on their ECG who benefit more and the longer the QRS, the worse the prognosis and the more likely that patient is to benefit from the device.
It is also important to mention that even if you don’t have ECG evidence of LBBB and a wide QRS on your ECG, it can develop with time and therefore although you may not be deemed suitable for BiV initially, you could be as time progresses and in one study it was found that 1 in 10 patients will develop LBBB in the first year of follow-up and therefore it is always a good idea to have a 12 lead ECG once every year because it is possible that you may be eligible for a BiV pacemaker which could in turn have a significant impact on quality of life and length of life.
So I hope you found this useful – I am sorry that I haven’t been able to do any vlogs for a few weeks – i had been away for a while to spend some time with my mother as it was coming up to a year since my father passed away and since i got back i have just been struggling with the backlog of work but i am slowly rediscovering my mojo so hopefully will be more regular with my videos. Thank you so much for your patience and I value each and everyone of you.