If you have a persistent, debilitating cough, it could be a viral infection that looks like the flu but is really a sign of heart disease. By Michael Lim

BOTH Miss A and Mr B had cough and breathlessness – one recovered and one did not. Coughing may be more than just the “flu”.

Miss A was only in her early 30s and she had been coughing for two months. Weeks of cough medication and a few visits to her doctors did not seem to cure the cough. She gradually became worse and felt breathless even at rest. She turned up at my clinic recently and it was obvious from her coughing, breathlessness and fast heart rate that she had a serious heart problem.

An ultrasound examination of the heart confirmed my worst fears – her heart was severely swollen and was barely pumping. Given that she had no family history of heart disease, it was almost certain that her heart had been savaged by a virus. Her delay of two months, through no fault of hers, had resulted in further deterioration of her heart, making it more challenging to treat her.

Mr B was more fortunate. He saw me within a week of coughing and breathlessness. Like Miss A, he was breathless even at rest. His heart was severely swollen and his heart pump was poor; he had viral infection of his heart (viral myocarditis). He was started on treatment and progressively improved. Much to my delight, after one year of treatment, his heart size and his heart function became normal.

Viral myocarditis presents typically like flu and is caused mainly by viruses that affect the upper respiratory tract. It is believed that five to 20 per cent of sudden deaths in young adults are caused by viral myocarditis.

While some patients, like Mr B, do get complete recovery, others, like Miss A, may get permanent damage of the heart muscle. Death can result from severe weakening of the heart pump or sudden unexpected life threatening heart rhythm abnormalities.

Long-term outlook Determining the long-term outlook for patients with myocarditis is important. A German study published in February this year in the Journal of the American College of Cardiology found that the finding of the presence of scarring of the heart muscle on cardiac magnetic resonance (CMR) imaging was the best independent predictor of poor outcome in patients with viral myocarditis.

In their study of biopsy-proven viral myocarditis, no patients with a normal CMR study died whereas for those with scarring, over a period of about five years, almost 20 per cent died, of which almost 10 per cent had sudden death.

For those with severe damage of the heart with extremely poor pump function, as in Miss A’s case, heart transplant is a considered option. But the reality is that there are very few donors available. Another option currently available is the use of a mechanical pump inserted into the heart called a “left ventricular assist device” which helps the heart to pump blood. The cost for such treatment can be prohibitive and can amount to a few hundred thousand dollars. Even then, it is not meant to be a permanent solution.

It has been more than a month since treatment was started, and Miss A is now able to go back to work and go about most of her usual activities without any significant limitation. Her heart swelling has decreased and her heart function has improved. Although there is still some distance to go towards improving her heart function, at least, it does not appear that she will need a heart transplant or left ventricular-assist device in the near future.

Who is more susceptible to viral infection of the heart? What is it that makes someone like Miss A susceptible to viral myocarditis? Why do some who get viral infections get myocarditis and others do not? Research is helping us to understand which genetic or environmental factors can determine which individuals infected with the same virus remain well or develop severe damage to the heart.

In Keshan county of Heilongjiang province in China, children and young women were found to be afflicted with severe damage to the heart, often resulting in death. The condition, named Keshan disease, was found to be caused by a combination of dietary deficiency in selenium and the presence of a strain of Coxsackie virus.

Mice studies showed that a normally harmless strain of Coxsackie virus underwent mutation and became virulent after infecting selenium-deficient mice. This suggests that a change in viral virulence can occur in some individuals in the presence of external factors such as selenium deficiency. This disease peaked in the 1960s and was eventually reduced with selenium supplements.

The presence of a “door”, such as the Coxsackievirus-adenovirus receptor (CAR) on the surface of the cell which allows the virus to enter the cell, appears to be associated with an increase in susceptibility to viral infection of the heart.

A 2009 German study published in the Journal of the American College of Cardiology demonstrated that the presence of this “door” enables viruses to enter into the heart muscle cells and in the absence of this “door”, there was no significant evidence of viral damage of the heart after the viral infection despite the presence of infection of other tissues. The high prevalence of CAR in the heart at young ages may perhaps account for the higher susceptibility to myocarditis in children. As we learn more, newer methods are being explored to reduce this susceptibility to viral myocarditis.

Do not exercise if you have the flu Most doctors will routinely advise patients against exercising if they have the flu. One the reasons is that, occasionally, the virus may attack your heart with dire consequences. Therefore, if you get the flu but have persistent cough and breathlessness, it may be more than just your regular flu – it may be viral myocarditis.