I have been debating writing this post for weeks and have successfully deferred it in favor of other posts. This morning, following a conversation with Dr. Mustafa Ahmed, I decided to tackle the subject. My hesitance was borne from the magnitude of the subject. For now, the approach will be for a general overview of diastolic heart failure and we can get more specific in future posts should the need arise.
Before we go to far, there are two definitions that we should address.
Heart failure – This is the clinical syndrome where your body is unable to distribute enough blood flow to meet your body’s needs, or at least it cannot meet those within normal parameters and pressures. Heart failure is often called congestive heart failure or CHF for short.
Ejection fraction – This is the percentage of blood that your heart pumps with each heart beat. A normal heart usually evacuates a little more than half of its volume with each heartbeat. This means that the ejection fraction will be greater than 50%. Most of the time when your physician is speaking of ejection fraction, he/she is referring to the left ventricle.
Diastolic heart failure, is when you have heart failure* with a near normal (preserved) ejection fraction**. This type of heart failure is related more to the heart’s inability to relax than to its inability to squeeze. Diastole is the period of the cardiac cycle when the heart relaxes and blood enters the heart before being ejected. It is somewhat like loading a cannon. Each time the cannon is fired it has to be reloaded. The internal combustion engine of your car may be a more apt analogy but I will need to think about it further. Regardless, what would happen if you had trouble reloading your cannon? You would have all kinds of trouble wouldn’t you?
A heart with diastolic dysfunction is extra-stiff much like the brand new balloon that my kids want me to inflate. I have to huff and puff extra hard to get air into it. The brand new balloon requires a higher than normal pressure to appropriately fill it just like an extra stiff heart. The stiff heart requires more time to fill with blood and sometimes requires higher intracardiac pressures (pressures within the heart). Faster or irregular heart rates (such as atrial fibrillation) can negatively affect your heart’s ability to function at peak efficiency.
There are two main characteristics in diastolic heart failure: 1) you have to have heart failure. 2) you have a near normal ejection fraction in the setting of a stiff heart.
The diagnosis of heart failure is primarily clinical and is characterized by the following:
- Shortness of breath
- Difficulty lying flat because of shortness of breath
- Waking in the middle of the night gasping for breath. Often times you may want to sit up in bed.
- Persistent cough or wheezing
- Edema or fluid build-up
- Weakness or easy fatigue
- Poor appetite or nausea
- Abnormally fast heart rate.
- Enlarged neck veins suggestive of elevated pressure within your heart
- An enlarged heart or signs of fluid on a chest x-ray.
If your doctor is unsure about the diagnosis, then additional testing such as plasma BNP or NT pro-BNP, and cardiopulmonary exercise testing may be in order.
The second requirement is confirmation of a normal or near normal ejection fraction. There are a number of methods to evaluate the ejection fraction including echocardiography, nuclear testing, ventriculography at the time of catheterization, cardiac MRI and cardiac CT. Findings such as thickened heart walls, an enlarged left atrium and stiff heart muscle support the diagnosis. Other causes of heart failure not directly related to the muscle must be excluded. Echocardiography is the most utilized tool because of its accessibility, ability to evaluate the aforementioned supportive findings and lack of radiation.
Treatment of Diastolic Heart Failure
If you have been diagnosed with diastolic heart failure there are four main objectives for treatment:
- Excellent control of your blood pressure
- If you have atrial fibrillation or an abnormally fast heart rate, your heart rate should be controlled.
- Treat your symptoms of heart failure
- If you have significant coronary artery disease then blockages should that are contributing to your symptoms should be addressed.
Blood pressure control
Your heart is like a muscular engine built around a connective tissue chassis. It is powerful and has almost unimaginable endurance. It responds to work and stress by getting stronger. High blood pressure is like lifting weights for your heart. On the surface, that seems like it should be a good thing. Unfortunately your heart doesn’t like lifting weights is prefers yoga. Lifting the heavy load of blood pressure does the same thing to your heart that it does to your biceps. The muscle gets bulky (left ventricular hypertrophy or LVH) and inflexible (impaired relaxation). If you recall from part 1 of this post, stiffening of the heart is what gets you into trouble. As a matter of fact, high blood pressure of hypertension is one of the, if not the leading cause of diastolic dysfunction.
The good thing is that all is not lost. There is solid evidence that improving ones blood pressure can lead to regression of LVH. Some medicines such as angiotensin II receptor blockers (ARBs), calcium channel blockers and angiotensin converting enzyme (ACE) inhibitors seem to lead to regression faster than other classes. Other classes such as diuretics and beta-blockers are also effective but to a lesser degree. There is no strong evidence that faster regression leads to improved outcomes.
The most important thing for you is to get your blood pressure under control. The Joint National Committee regularly updates their recommendations on how to best control blood pressure. There are extensive guidelines as to what medicines are most helpful in certain medical conditions such as diabetes and coronary artery disease. For those of you with diastolic heart failure, your medication regimen will be based largely on any other co-existing medical conditions. When it comes to diastolic heart failure, the journey is probably less important than the destination.
Heart rate control
We have already learned that the heart fills with blood during diastole. When the heart becomes stiff, it needs more time to fill. Diastole is indirectly related to heart rate so faster heart rates mean shorter filling times. This is why tachycardia, or an abnormally fast heart rate, is not well tolerated in this condition. This is magnified in conditions such as atrial fibrillation or atrial flutter. Usually, the atria and ventricles work in concert. The atria are essentially reservoirs that sit above the ventricles (the heart’s main pumping chambers). They intermittently pump blood into the ventricles to help the ventricles fill with as much blood as possible. This results in a more efficient diastole and happier ventricles. These conditions often result in tachycardia and more importantly; the coordinated squeeze is also lost. In the setting of diastolic heart failure, since ventricular filling is already compromised, this can have a profound effect. It becomes doubly important to have a reasonably slow heart rate to allow for optimal filling. The medicines used most commonly to slow your heart rate fall under the categories of beta-blocker and calcium channel blocker. Sometimes in atrial fibrillation or flutter we have to go a step further and take actions to return you to a normal heart rhythm.
Treat your symptoms of heart failure
Treatment for diastolic heart failure is primarily directed at treating the “congestion” of congestive heart failure. These symptoms are related to higher than normal pressures within your heart and lead to the classical symptoms including shortness of breath, edema and fatigue. Management of these symptoms relies heavily on diuretic use to help your body eliminate excess fluid. Limiting salt intake is of critical importance (please review Dr. Guichard’s discussion on salt in heart failure). Lowering an abnormally high blood pressure and treated other correctable causes such as aortic stenosis are also beneficial. Long-term exercise has been shown to improve diastolic function and improves the functional capacity of persons with abnormal diastolic function
Ischemia is bad
Coronary artery disease where a heart blockage causes significantly decreased blood flow can lead to varying levels of ischemia in the myocardium. Ischemia is a shortage of blood flow that results in insufficient oxygen and nutrient transport to maintain normal metabolism. Relaxation of the myocardium is an energy driven process, meaning that it requires work to relax (kind of oxymoronic). Coronary blockages can thereby affect the heart ability to relax and should be aggressively treated.
Diastolic heart failure is a complex entity that is not always intuitive. A good low salt diet, blood pressure control and regular exercise will go a long way to controlling many of your symptoms. Your doctor will be able to help you determine what the likely cause of your diastolic disease and devise a treatment plan to combat it.