heart failure and diabetesheart failure and diabetes

Heart Failure and Diabetes

Heart failure is a very prevalent and serious complication noticed in diabetic patients. Before we try to understand the relationship between heart failure and diabetes, we must know the basic functioning of the heart and also what it means by heart failure. A normal healthy heart is a strong muscular organ that acts as a pump. It is slightly larger than the size of a fist. This organ pumps blood continuously through the circulatory system. The heart has 4 chambers – 2 upper chambers called the atria and 2 lower chambers called the ventricles. The right atrium takes in oxygen-depleted blood from the rest of the body and sends it through the right ventricle where the blood becomes oxygenated in the lungs. Oxygen-rich blood travels from the lungs to the left atrium and then to the left ventricle, which pumps it to the rest of the body. For the heart to function properly, the 4 chambers should beat in a well-synchronised and organised manner. 

The term heart failure does not mean that your heart has stopped functioning. Whereas it is a condition that develops when your heart doesn’t pump enough blood for your body’s needs. This can happen if your heart can’t fill up with enough blood or is too weak to pump properly. Heart failure is a chronic progressive condition in which the heart muscle is unable to pump enough blood to meet the body’s needs for blood and oxygen. At first, the heart tries to make up for this by enlarging in size and thereby trying to contract more strongly. By trying to develop more cardiac muscle mass and also by trying to pump faster to increase the heart’s output. It also tries to compensate by narrowing the blood vessels to keep the blood pressure up and also by diverting blood away from less important tissues and organs like the kidneys and the brain. These temporary measures mask the problem of heart failure but do not solve it.

Heart failure continues and worsens until these compensating processes no longer work. Eventually, the heart and body just can’t keep up and the person experiences fatigue, respiratory difficulty etc. Being diagnosed with heart failure is not the end of life. It can be managed. Due to a lack of awareness about the disease, patients do not consult the doctor at the right time. Treatment usually begins too late. A famous cardiologist once said – “Our body is a great miracle and our heart is designed to pump tirelessly from the moment even before we are born, till the person dies.” The first signs of life are recognised on the ultrasound by checking the foetal heart movement. Many reasons may weaken it leading to heart failure and often it is not easily reversible, but can be managed if acted at the right time. 

Now we must try to understand the relationship between diabetes and heart failure. Why heart failure is more prevalent in diabetic patients? Patients with diabetes mellitus have double the risk of developing heart failure. Beyond the structural and functional changes in the heart in diabetic patients, a complex underlying and interrelated pathophysiology exists. Despite, using good anti-diabetic medications to lower hyperglycemia in type 2 Diabetes Mellitus, the high prevalence of heart failure persists. This, therefore, raises the possibility that additional factors beyond glycemia might contribute to the increased risk of heart failure in diabetes mellitus.

Dysregulation of many cellular mechanisms like oxidative stress, inflammation, endoplasmic reticulum stress, aberrant insulin signalling, accumulation of advanced glycation end products, altered autophagy, changes in myocardial substrate metabolism, lipotoxicity and altered signal transduction etc have been described. The increased incidence of heart failure in diabetic patients persists, even after adjusting for the risk factors such as age, hypertension, hypercholesteremia and coronary artery disease. Thus the term diabetic cardiomyopathy was initially used to describe ventricular dysfunction in the absence of coronary artery disease and hypertension in diabetic patients. However, now it has been broadened to describe the increased vulnerability of the myocardium to dysfunction that characterizes individuals with diabetes mellitus. 

Heart failure can be ongoing or chronic or it may start suddenly or acute. What are the common symptoms of heart failure? Signs and symptoms of heart failure include 

  • Shortness of breath with activity or when lying down
  • Swelling in legs, ankles and feet
  • Fatigue or weakness
  • Rapid or irregular heart beat
  • Persistent  cough or wheezing with white or pink blood in mucus
  • Inability to exercise
  • Swelling of abdomen
  • Rapid weight gain due to fluid retention 
  • Decreased alertness and difficulty in concentration 

What are the commonest causes for heart failure?

The commonest causes that lead to heart failure include 

  • Coronary heart disease, i.e. acute or myocardial infarction, atherosclerotic heart disease or past history of myocardial infarction etc. 
  • Uncontrolled hypertension 
  • Valvular heart diseases
  • Heart muscle disease such as dilated cardiomyopathy, hypertrophic obstructive cardiomyopathy, myocarditis etc
  • Congenital heart diseases, 
  • Diabetes mellitus
  • Severe lung disease
  • Obesity
  • Sleep apnea syndromes
  • Severe anemia
  • Hyperthyroidism 
  • Cardiac Arrhythmias etc. 

How do you classify or grade a heart failure?

Heart failure is usually classified by New York Heart Association (NYHA) into class 1, 2, 3 and 4. Class 1 heart failure is when there are no heart failure symptoms. In class 2 heart failure, daily activities can be done without difficulty but exertion causes shortness of breath and fatigue. The patient finds it difficult to complete everyday activities in class 3 heart failure. Whereas in class 4 heart failure, breathlessness occurs even at rest. 

How does one diagnose heart failure?

Apart from a detailed history and thorough physical examination, heart failure is diagnosed based on various clinical signs and symptoms in the patient. Symptoms are usually divided into major and minor criteria. So the major criteria include acute Pulmonary Edema, Cardiomegaly, Neck vein distentions, Orthopnea or breathlessness at rest, Hepatojugular reflex, Pulmonary crepitations or crackling sounds in the base of lungs, third heart sound or S3 gallop. And the minor criteria include swelling in the feet, breathlessness on exertion, enlarged liver, cough at night time, pleural effusion, tachycardia or increased heart rate of more than 120 beats per minute.  

Tests to be done to diagnose heart failure?

The commonest blood test done to diagnose heart failure include blood sugar, a complete lipid profile, c-reactive protein, lipoprotein (a), BNP and Pro BNP, Troponin T. Apart from the blood tests, the other investigations which should be done include an electrocardiogram or ECG, chest X-ray, echocardiogram, exercise stress test etc. 

In some patients, further advanced tests like coronary angiogram, radio nuclei ventriculography, MRI imaging of the heart, etc will have to be conducted to look for blockages in the coronary arteries to see how well the heart muscles supply blood, how well the heart chambers are functioning, whether part of the heart muscle is damaged by heart attack and also to assess the heart musculature, walls and chambers and how well blood flows through your heart and major vessels respectively.