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The ‘other’ heart disease

Ask a reasonably well-educated adult to define heart disease and the first words you are likely to hear are “heart attack!”

In common parlance, heart disease and heart attack have become nearly synonymous. Myocardial infarction represents one of the most frequent, and arguably most dramatic, manifestations of cardiac pathology, but it is just the gleaming tip of the big iceberg that is heart disease.

This melding of heart attack with heart disease in the popular imagination masks the presence of another important cardiac pathology – heart failure or what I call “the other” heart disease, one that generates less fanfare, fewer headlines and remains under the public’s radar.

Heart failure, whose hallmark feature is a heart muscle too weak or too stiff to pump blood effectively, affects more than 23 million people globally. Fuelled in part by the rising tides of hypertension, diabetes and people living longer, both the prevalence and incidence of heart failure are steadily increasing, and so is the number of people who succumb to it.

We, as clinicians, ought to do a better job in educating people about its existence, its symptoms and the toll it takes for heart failure is not a looming epidemic, but a de facto pandemic. Altering the course of this global health crisis requires parallel efforts in the lab and in clinic.

Heart failure is not a single disorder, but a syndrome dauntingly complex in its etiology and course. It can stem from inherited pathologies of the cardiac muscle or develop as the end-result of longstanding, untreated hypertension, poorly controlled diabetes, malfunctioning heart valves or the after-effects of multiple heart attacks. It may be the price we pay for medical advances that have allowed many to live to an age when their hearts start to give out.

Heart failure represents one of medicine’s greatest success stories and one of its most disappointing failures. We have made great strides in managing heart failure’s acute manifestations, but remain woefully underprepared and mal-equipped to avert its onset and diagnose it early, before the disease takes serious toll on the heart and other vital organs.

Clinician-scientists will have to ramp up their quest for highly sensitive and specific biomarkers that herald the onset of the disease before it produces clinical signs

We have made some critical progress in slowing down the irreversible march of the disease with an armamentarium that includes both pharmacological and interventional approaches. Pacemaker-based resynchronization therapy and implantable cardioverter defibrillators are now mainstays in the treatment of advanced heart failure. For those with end-stage disease, we use ventricular assist devices, mechanical pumps that serve as bridges to transplant and, increasingly, as “destination” or permanent therapy. Albeit cautiously, we are now starting to use stem cells to regenerate heart muscle – an approach deemed science fiction not even two decades ago. These are all laudable achievements, humbling feats of scientific acumen and clinical creativity, which have prolonged patients’ lives.

All our high-tech gadgets and dizzyingly complex critical interventions notwithstanding, we lag behind in prevention, early detection and individualised therapy – the three Holy Grails of medicine. Finding them will take synergistic efforts by primary care clinicians, basic and translational scientists, and public health experts.

While we have unraveled the causes of most forms of heart failure and described the crude mechanics behind them, we still don’t understand the precise molecular mechanisms that drive the earliest and subtlest shifts in cardiac cell function, which over time culminate into clinical disease. I am confident that in the next 20 years, basic and translational research will unravel these important molecular mechanisms, and these insights will become the foundation for therapies that prevent heart failure from progressing into overt disease in the first place.

More often than not, heart failure tiptoes its way in. It can be an insidious disease, with an often unrelenting course. Primary care clinicians remain the frontline detectors of the first and subtlest signs of the disease – vague fatigue, mild exhaustion, a persistently elevated heart rate. But we now know that heart failure begins long before its first clinical symptoms emerge. Therefore, clinician-scientists in academic centres across the globe will have to ramp up their quest for highly sensitive and specific biomarkers that herald the onset of the disease before it produces clinical signs. Such a biomarker could become part of the standard metabolic panel during routine physicals, alerting a physician of the earliest molecular malfunctions in the cells of the cardiac muscle, well before the first physiological signs of the disease emerge.

PRECISION-TARGETED TREATMENT

No two patients with heart failure are the same. We already know that patients metabolise drugs differently and respond differently to treatment – variances rooted in gender, race and individual biology. But we are now beginning to appreciate even subtler differences in the genesis of cardiac disease. Heart failure is caused by a constellation of genetic predispositions, epigenetic modifiers, physiologic malfunctions, lifestyle influences and social behaviors. The degree to which each one of these factors contributes to disease onset varies from one person to the next. Our ongoing research into the genetic and epigenetic influences that trigger heart failure holds the promise of individualised therapies that will precision-target pathologies on a patient-specific basis.

And as we move forward, all of us, whether we are primary care clinicians practising on the frontline, cardiologists treating patients in specialty practices or clinician-scientists working in research hospitals, must remember to ask the fundamental questions in medicine: “Why this patient? Why this disease? Why now?”


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