On May 5, the Ministry of Health (MOH) announced that a 44-year-old male Bangladeshi national (Case 16370) had passed away earlier that day.

However, his death was not classified as a Covid-19 death, as the cause was stated to be acute myocardial infarction, or a heart attack.

Singapore currently has 20 recorded Covid-19-linked deaths, but there have so far been an additional six Covid-19 patients reported to have died from causes deemed not to be complications from their Covid-19 infection.

Why are they not counted as Covid-19 deaths by the authorities? The answer, perhaps, lies in how Covid-19 deaths are classified according to the World Health Organisation (WHO) and MOH.

Significantly, though, important scientific evidence has been surfacing about the correlation between Covid-19 infection and the development of heart and blood problems amongst even younger patients, similar to the cases we have seen in Singapore recently.

But first, let's recap what we know about the passing of the six Covid-19 patients in Singapore who have not been classified as Covid-19 deaths.

Singapore's non-Covid-19 deaths

As of May 7, Singapore’s Covid-19 deaths have all been among the more elderly, with the youngest thus far being Case 703, 58-year-old Singaporean Salha Mesbee.

However, the Covid-19 patients who have died of causes deemed to not be Covid-19 have been notably younger on average. Other than one 80-year-old patient, the rest were all in their 30s or 40s when they passed away.

They have also all happened to be foreigners.

Other than Case 8190, Alagu Periyakarrupan, who died of multiple injuries consistent with those resulting from a fall from height, and Case 3381, whose cause of death was only listed as "causes not relating to Covid-19", the other four patients died from problems linked to the heart.

And what is worth noting is that studies in the U.S., China, and elsewhere have found an abnormally high prevalence of situations like these four patients — heart problems and blood clotting amongst younger Covid-19 patients, indicating they could be linked to the viral infection.

How deaths of Covid-19 patients are classified

So, how are the cases in Singapore classified, and how was the decision made to not classify the other Covid-19-positive patient deaths as Covid-19 deaths?

The World Health Organization's (WHO) guidelines for classifying Covid-19 as the cause of death, updated on Apr. 20, defines a death due to Covid-19 as the following:

"A death due to COVID-19 is defined for surveillance purposes as a death resulting from a clinically compatible illness, in a probable or confirmed COVID-19 case, unless there is a clear alternative cause of death that cannot be related to COVID disease (e.g. trauma).

There should be no period of complete recovery from COVID-19 between illness and death.

A death due to COVID-19 may not be attributed to another disease (e.g. cancer) and should be counted independently of preexisting conditions that are suspected of triggering a severe course of COVID-19."

The WHO provides guidelines on how to record the chain of events and comorbidities — additional conditions that were detected in the patient along with Covid-19, in these cases — on the death certificate, as it is of the view that "it is important to record and report deaths due to COVID-19 in a uniform way".

The WHO writes that specification of the causal sequence leading to death is important.

For example, for cases where Covid-19 causes pneumonia and fatal respiratory distress, both pneumonia and respiratory distress should be listed under "cause of death", along with Covid-19.

"Certifiers should include as much detail as possible based on their knowledge of the case, as from medical records, or about laboratory testing," wrote the WHO.

In addition, if the deceased patient had any existing health conditions, such as coronary artery disease, chronic obstructive pulmonary disease, and diabetes or disabilities, they should be reported on the medical certificate under "Other significant conditions contributing to death".

Here is an example from the WHO:

In this case, suspected Covid-19 is the underlying cause of death with pneumonia and acute respiratory distress syndrome, which were likely brought on by the Covid-19 infection also listed as causes of death.

The patient's other health conditions — coronary artery disease, type 2 diabetes, and chronic obstructive pulmonary disease — are listed not as causes of death but other significant conditions contributing to death.

However, the WHO also gives the following as an example of how to record when a death may have been influenced by Covid-19, but was caused by another disease or an accident:

The WHO noted that patients with Covid-19 may die from other conditions, such as myocardial infarction (heart attack), as in the case of two of Singapore's deaths — Cases 4754 and 16370.

"Such cases are not deaths due to COVID-19 and should not be certified as such," wrote the WHO.

In this example, Covid-19 is considered a "significant condition contributing to death" but not a "cause of death".

And so why does MOH count these six as non-Covid-19-caused or related deaths?

Speaking on Friday (May 8) about how a Covid-19 patient's cause of death is determined, MOH's Director of Medical Services Kenneth Mak explained that the government follows the information provided to them by medical authorities, and stressed that Singapore is "quite transparent" with its announcements of deaths:

"So, in relation to Covid-19 cases that unfortunately have passed on, our approach really is first to ask ourselves, 'Is this directly attributable to Covid-19 infection or complications related to Covid-19 infection?'

In which case, if they are, we will report them as such.

And this comes out in our press statement that comes out every day. In fact, we are quite transparent in announcing and reporting all the deaths that we have, even if they were not due to Covid-19 infection, then they would be reported still.

But we will not necessarily ascribe them to Covid-19 unless we have been informed by the medical authorities, whether the doctors attending to the patient, or the coroner, if these were made coroner's cases, if they were telling us directly that these were deaths attributable to Covid-19 infection, then we will be reporting them as such."

Responding to Mothership enquiries, an MOH spokesperson gave the following statement on May 9:

"The Ministry of Health reports all deaths in patients infected with Covid-19. However, we add to the Covid-19 death count the cases where the attending doctor or pathologist attribute the primary or underlying cause of death as due to Covid-19 infection.

This has been our consistent practice, applied for both Singaporeans and foreigners in Singapore. It is consistent with international practice for classifying deaths.

In 2018, 86 male foreign workers aged 25 to 59 passed away due to heart disease in Singapore."

Research on Covid-19 and its link to heart problems

That being said, there is now a growing body of evidence showing links between other health issues, such as heart attacks and strokes, and Covid-19.

This indicates that there could possibly be more to the stories of these patients whose deaths are classified as non-Covid-19-caused.

A number of studies and observations have noted that the virus has the ability to lead to heart problems and blood clotting, even amongst those with no medical history, with a worrying trend of young people suffering strokes and heart attacks.

Research correlating Covid-19 with heart problems has been around since early in the viral outbreak.

A study conducted on patients in Wuhan in January found that of 41 patients hospitalised with Covid-19, five of them, or 12 per cent, showed signs of cardiovascular damage.

Other reports from China published in February and March also supported the hypothesis that Covid-19 can cause damage to the cardiovascular system, including the heart.

A study published in March, led by Dr. Zhibing Lu at Zhongnan Hospital of Wuhan University, found that out of 187 Covid-19 patients, 20 per cent had some evidence of heart damage.

Despite many not having any underlying heart disease, to the best of their knowledge, many of them showed abnormal electrocardiograms (the visual display of their heartbeat).

Amongst these patients with abnormal heartbeats, their risk of death was four times higher than patients without heart complications.

According to an article published in the Harvard Gazette, Harvard Medical School physician-scientists and cardiologists at Brigham and Women's Hospital Peter Libby and Paul Ridker explained four possible ways that Covid-19-related heart injury could occur:

1. Those with pre-existing heart conditions are at greater risk of developing severe cardiovascular and respiratory complications from Covid-19. Research has also shown that respiratory infections such as the flu could bring about heart attacks.
2. People with previously-undiagnosed heart disease could have previously-silent cardiac symptoms be revealed by Covid-19. Fever and inflammation make the blood more prone to clotting, while simultaneously disturbing the body's ability to dissolve blood clots.
3. Covid-19 infection could cause a mismatch between oxygen supply and oxygen demand to the heart, which could cause some people to experience heart damage similar to that of heart attack injury.
4. Some Covid-19 patients who were previously healthy and had no underlying cardiac problems could develop sudden inflammation of the heart muscle due to the virus directly infecting the heart.

As quoted in the New York Times, Dr. Scott Solomon, a cardiologist at Harvard Medical School, said, "Myocarditis [an inflammation of the heart muscle] can likely be caused either by the virus itself, or the body’s immune and inflammatory response to the virus."

Also linked to cases of blood clotting and strokes

The Washington Post published an article on Apr. 23 digging into the link between Covid-19 and blood clotting complications.

It described doctors in the U.S. having issues with their patients developing blood clots, despite being put on coagulants, and that there had been hints that blood problems amongst Covid-19 patients had also been an issue in China and Italy.

Data from the Netherlands and France found that 31 per cent and 69 per cent, respectively, of Covid-19 patients admitted to the ICU developed blood clots in the deep veins of their legs or in their lungs.

The research from France also found that nearly one-quarter of the patients were diagnosed with pulmonary embolism — the sudden blockage of a major blood vessel in the lung.

The prevalence of blood clotting has also been linked to the number of stroke cases amongst young and middle-aged people in the U.S., according to another Washington Post article.

This one reported that Covid-19 patients appear to be mostly experiencing the most deadly type of stroke — large vessel occlusions (LVOs), which are main blood-supply arteries to the brain.

Many researchers think that strokes in Covid-19 patients could come from blood clots being created by the blood problems arising from Covid-19 infection.

In a letter to the New England Journal of Medicine, a team of doctors from the Mount Sinai Health System in Manhattan, New York City, presented the details of five patients under the age of 50 who had suffered large-vessel stroke over a two-week period between Mar. 23 to Apr. 7.

In comparison, they wrote, over the previous 12 months, their service had treated an average of only 0.73 patients per two weeks who were under the age of 50 and had suffered large-vessel stroke, or less than two per month.

All five of the stroke patients in their study — aged 33, 37, 39, 44, and 49 — also tested positive for Covid-19.

Only one had a history of stroke, and two of the patients had no medical history at all.

Speaking to CNN, one of the members of the team, neurosurgeon Thomas Oxley, said:

"Our report shows a seven-fold increase in incidence of sudden stroke in young patients during the past two weeks.

Most of these patients have no past medical history and were at home with either mild symptoms (or in two cases, no symptoms) of Covid."

Despite this, the Washington Post reports that one patient died and two were still hospitalised as of Apr. 26. One patient was released to rehabilitation, and the final patient was discharged under the care of his brother.

Out of the five patients, reported the Washington Post, only the 33-year-old has the ability to speak.

Why does it matter how the deaths are classified, anyway?

Now that we have a little more understanding the research into links between heart attacks, strokes, blood clotting, and Covid-19 infection, it's worth looking into why all this even matters.

While researchers have yet to be able to develop concrete conclusions about the exact effects of Covid-19 on patients' hearts and blood and why those effects may occur, it is important to keep paying attention to the studies and observations that are still being made and reported about correlations between the viral infection and other health issues and causes of death.

The way deaths are classified does matter for a number of reasons, one of which, for instance, is the types of insurance that can be claimed by a deceased person's family, if at all.

In addition, the families of Covid-19 patients who succumb to the virus are eligible for monetary relief of between S$10,000 and S$30,000, through the Courage Fund Covid-19 Relief Schemes.

It follows, then, that the designation of a Covid-19 patient's death as being due to Covid-19 or to another condition could affect the eligibility of the patient's family for this relief.

Local non-governmental organisation Humanitarian Organization for Migrant Economics (HOME) published a statement on May 7 calling for the Singapore government to be clearer about the rationale behind how deaths are recorded.

"Clearer explanations and reporting deaths due to comorbidities as part of daily situation reports will provide clarity on the parameters which the authorities are using to define whether a death is caused by the disease," it said.

HOME also argued that sharing what knowledge about the virus and infection is available with the migrant worker population could help ease their fears:

"... It will be reassuring to our migrant workers to inform them what is known, rather than to state, without clear reasoning, why the deaths of their compatriots have not been classified as having been caused by Covid-19 when they have been diagnosed with the same."

"A lack of information from the authorities about how the virus works will only compound this problem as we may be left with more deaths in our migrant worker community due to undetected underlying conditions," the statement said.

According to an article in Scientific American on Apr. 6, understanding the medical mystery of whether and how Covid-19 affects the heart, and what to do about it, could have immense impact on how patients are dealt with too:

"That could change the way doctors and hospitals need to think about patients, particularly in the early stages of illness.

It also could open up a second front in the battle against the Covid-19 pandemic, with a need for new precautions in people with preexisting heart problems, new demands for equipment and, ultimately, new treatment plans for damaged hearts among those who survive."

It also quoted Dr. Ulrich Jorde, head of heart failure, cardiac transplantation and mechanical circulatory support for the Montefiore Health System in New York City, who said:

"It’s extremely important to answer the question: Is their heart being affected by the virus and can we do something about it.

This may save many lives in the end."

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Mothership Explains is a series where we dig deep into the important, interesting, and confusing going-ons in our world and try to, well, explain them.

This series aims to provide in-depth, easy-to-understand explanations to keep our readers up to date on not just what is going on in the world, but also the "why's".

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Top photo by Roslan Rahman/AFP via Getty Images.