What is heart failure? (part two)Sunday, February 28, 2021
Ernest Madu and Paul Edwards
Today, we continue our discussion on heart failure and will look at the diagnosis of heart failure, diagnostic tools for heart failure and explore how the risk of heart failure can be decreased.
Like most clinical conditions, the evaluation of heart failure begins with a history and physical examination. Broadly speaking, heart failure symptoms can be divided into symptoms of “congestion” and symptoms of “low output”. Congestion relates to symptoms of fluid accumulation in the body and includes swelling of the legs, abdomen and in rare cases the whole body. Fluid can also accumulate in the lungs causing shortness of breath with activity, when lying in bed at nights or in severe cases at rest. Low output symptoms are related to inadequacy of blood flow for the tissues of the body. These symptoms can include weakness, lack of energy, exertional intolerance, dizziness, etc. Patients may sometimes have associated symptoms of cardiac dysfunction including chest pain, palpitations, etc. Physical examination is useful in confirming evidence of fluid accumulation or signs of cardiac dysfunction.
The difficulty with the clinical diagnosis of heart failure is that there are conditions that can mimic the historical and examination findings of heart failure. Renal and hepatic diseases commonly are associated with symptoms of swelling and lack of energy. Morbid obesity can present with exertional intolerance and findings of edema. An interesting, although uncommon conundrum is the diagnosis of heart failure in the pregnant female. The normal symptoms of pregnancy can mirror those of heart failure. Given these challenges, an accurate diagnosis of heart failure will depend on finding abnormalities of the structure and function of the heart or evidence that the pressures in the heart are elevated above normal. This usually is done with imaging of the heart.
What kind of testing is done to diagnose heart failure?
As noted above the first question is “Is the structure and function of the heart normal?”. The most common way that this question is answered is with the use of echocardiography which uses ultrasound waves to image the structure and function of the heart. The size of the heart chambers can be measured, the pumping function of the heart can be assessed, indirect measures of the pressures in the heart chambers can be made and cardiac valve function can be evaluated. For most patients with a question of heart failure an echocardiogram can quickly and reliably either confirm or exclude the diagnosis. Other advantages of echocardiography are its relatively wide availability, safety, and portability. One potential downside of this technique, however, is that it can be difficult to image very obese patients or patients with significant chest abnormalities. Echocardiography does require technicians/physicians who are trained in image acquisition and interpretation.
The heart can be imaged using other modalities. Cardiac magnetic resonance imaging is used with increasing frequency in the developed world. It does offer some advantages over echocardiography in that it can allow for characterisation of the myocardial tissue, visualisation of the heart arteries and evaluation of blood flow to the heart. Cardiac CT imaging offers similar advantages. These techniques are substantially more expensive than echocardiography and require more sophisticated equipment and trained personnel. There is also limited availability in the Caribbean region. Cardiac catherisation is an invasive technique where catheters are passed from the arms or legs to the heart. Using this technique, the pumping of the cardiac chambers can be assessed and pressures with the cardiac chambers measured. Given its invasive nature it is not usually the initial test for heart failure but can be quite useful in many situations.
Other testing can add useful information but in and of themselves are not sufficient for accurate diagnosis. An electrocardiogram or ECG is commonly done on patients with suspected cardiac disease. This test is a recording of six seconds of the electrical activity of the heart. It can give an indication of potential issues with heart structure; however, a normal ECG does not necessarily mean normal heart function and an ECG can be abnormal with a structurally normal functioning heart. A chest X-ray is also commonly performed in the evaluation of the cardiac patients. This test can raise the question of heart enlargement and can also indicate fluid accumulation in the lungs. These findings are usually confirmed with some evaluation of cardiac structure, most commonly an echocardiogram. Blood tests can also be used to help with diagnosis.
A heart that is failing releases chemicals that can be detected in the blood stream. These include the Brain Natriuretic Peptides (BNP and NT-BNP). If these are found to significantly elevated, they are strong evidence that heart function is not normal. This can be quite useful when evaluating patients who are short of breath and it is unclear whether the cause is related to the heart or to the lungs.
What additional testing may be required after heart failure is diagnosed?
Once we have a firm diagnosis of heart failure the next important question to answer is why is the heart failing? Getting to the cause of the heart failure is useful in management of the patient. It is important to know if the cause of heart failure in any given patient is reversible. As we noted last week, heart failure is associated with high morbidity and mortality. In scenarios in which a reversible cause is found and heart function can be returned to normal patients do better over time. Given this when we diagnose a new patient with heart failure, we look for reversible causes. One of the most common causes of potentially reversible heart failure is coronary artery disease or blockages in the blood vessels that supply blood to the heart. If normal blood flow to the heart can be restored, heart function will in many cases improve. Therefore, patients who are at risk for coronary artery disease will often undergo cardiac catheterisation or advanced cardiac imaging to evaluate the coronary arteries. Other potentially reversible causes of heart failure include disease of the heart valves (both narrowed and leaking valves), cardiac inflammation, poorly controlled hypertension, alcoholism, cardiac arrhythmias, chemotherapeutic agents, over activity of the thyroid gland, etc. The additional testing that may be required will clearly be different in each individual patient.
Risk of developing heart failure?
Heart failure has many different causes. Some of these causes, unfortunately, cannot be prevented with current medical knowledge. The good news, however, is that in much of the developing and developed world coronary artery disease and hypertension are the two most common causes of heart failure and both conditions are very strongly related to lifestyle. Hypertension is a strong risk factor for the development of heart failure particularly when poorly controlled. As we have discussed in previous articles it is important to know your blood pressure numbers as hypertension is most often asymptomatic. Lifestyle measures including regular aerobic exercise, achievement, and maintenance of an ideal bodyweight, limiting salt and alcohol in the diet, and increasing intake of fruits and vegetables can reduce the risk of hypertension and improve hypertension control. These measures, in addition to avoiding smoking, will also decrease the risk of coronary artery disease. There are other less common causes of heart failure that we can certainly avoid. These would include alcoholism and drug abuse, particularly cocaine. In coming articles we will look at how heart failure is treated.
Dr Ernest Madu, MD, FACC, and Dr Paul Edwards, MD, FACC are Consultant Cardiologists at Heart Institute of the Caribbean (HIC) and HIC Heart Hospital
Dr Madu is a main TED Speaker whose TED talk has been translated into 19 languages, seen, and shared by more than 500,000 viewers. He has received the Distinguished Cardiologist Award, the highest award from the American College of Cardiology and has been named among the 100 most influential people in health care and among the 30 most influential in public health. A recipient of the Global Health Champion Award from the University of Pennsylvania, Dr Madu was past CEO of HIC and is currently the Chairman of IHS Holdings Ltd, an asset management company with interests in the USA, Africa, and the Caribbean.
Correspondence to info@ caribbeanheart.com or call 876-906-2107
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