Sunday July 9, 2006
Treating heart failure
BY Dr DAVID KL QUEK
PERHAPS the most important medicine for various types of heart failure is the class of drugs known as diuretics, which are otherwise known as water pills. The most widely used diuretic is frusemide (American furosemide, most commonly known as lasix), but others also used are bumetanide, spironolactone, amiloride, tiramterene, chlothalidone, hydrochlorothiazide, and so on.
These diuretics stimulate increased salt and water excretion by the kidneys (through a variety of mechanisms and different pathways), and thereby rid the excess fluid overload in the body.
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Foxglove is the source of heart drugs such as digitalis. Its effect in improving cardiac function was recognised by science in 1770s. |
However, because one of the necessary intra-cell salts (known as potassium) is also excreted together with the fluid, some decrease in the blood concentrations of this important chemical also takes place. Low potassium levels can lead to muscle cramps, and erratic and sometimes dangerous heart rhythms.
Thus some potassium salt replacement is usually also prescribed – or the patient is advised to take plenty of fruits which contain high amounts of potassium. Combining with or using a diuretic like spironolactone or amiloride or triamterene can help spare too much of potassium loss through the urine.
Other very important drugs now established for use in heart failure are those which counteract the hormonal excess associated with the syndrome. The Renin-Aldosterone-Angiotensin System (RAAS) is that system which has become over-stimulated in heart failure, to the point of harming the body’s preciously balanced organs such as the heart, the blood vessels, the kidneys.
Ace it
The most well established group of medicines that is now the anchor of heart failure therapy is the ACE (angiotensin converting enzyme) inhibitors. ACE inhibitors (ACEI) commonly available in Malaysia include captopril, enalapril, quinapril, perindopril, ramipril, fosinopril, lisnopril, and imidapril. These drugs have been shown over and over again to not only improve symptoms and quality of life, but also to improve survival and reduce chances of hospitalisation and dying. (These drugs are also very useful for treating hypertension, so they have a dual role to play in some patients.)
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American ginseng, Korean ginseng and gingko, are used frequently by many Asians to strengthen the heart, but their real or measurable effects are unknown. |
While a nuisance, this ACEI-induced cough is quite harmless, so patients can sometimes be taught to tolerate these extremely beneficial pills.
Another very closely related class of drugs for heart failure and hypertension are the Angiotensin or AT1-Receptor Blockers (ARBs) also known earlier as Angiotensin II Antagonists (AIIAs). Their use in heart failure is not as robustly studied as the ACEIs, but in cases where ACEIs are not tolerated, they are a useful replacement.
Besides, they have no cough side effects. Examples of useful ARBs for heart failure which have been shown to be beneficial in some patients include valsartan, candesartan, and losartan. These drugs are also slightly more expensive than ACEIs.
The combined use of these two classes of drugs for heart failure is not well-established, but for those with kidney impairment, better results have been shown.
Beta blockers
One upon a time, beta-blockers were considered an absolute contraindication for use in heart failure. This is because beta-blockers (which block the stress receptors of the heart and blood vessels against the onslaught of stress hormones such as adrenaline, noradrenaline) are also known to dampen down the contractile function as well as heart rate of the heart muscle.
This is no longer believed to be so because the excess stressors appear to injure the heart muscle and the circulatory system more than controlling its disproportionate activity.
Three drugs from this class have now been shown to be very beneficial in controlling some of the symptoms, signs as well as the final outcome of heart failure – paradoxically they also reduce hospitalisations and the chances of sudden dying. These include carvedilol, bisoprolol, metoprolol succinate (the last one is a once daily drug which is not available in Malaysia; the available metoprolol tartrate salt has not been shown to be beneficial).
These drugs should however be initiated by experienced physicians who would monitor heart failure patients very carefully in the early phase, where very small doses are commenced, and titrated upwards to the full proven dose where possible. Sometimes, worsening of heart failure can occur if the drugs are used carelessly without adequate supervision.
Foxy drug
What about digoxin? This is the oldest drug used for heart failure (or “dropsy” as it was then known), first as an herb derived from foxglove, since the late 1700s.
These days, as a heart stimulant, digoxin has limited use because of its low therapeutic threshold –meaning that its toxicity quickly develops over a narrow range of its dose, especially in the elderly, the very thin, and those with kidney impairment.
It is still used as an adjunctive medicine with a diuretic, particularly in those with an erratic heart rhythm (atrial fibrillation), those with enlarged hearts, and those with low ejection fractions, where it has been shown to reduce hospitalisations and improve some symptoms.
Survival however is not changed or prolonged with digoxin therapy. However, when one is already on this drug, one should not unilaterally withdraw its use, because one major study has shown that withdrawal of digoxin can lead to worse outcome than when continuing with its therapy.
Important to treat other coexisting conditions
Managing heart failure must take into account coexisting disorders such as hypertension, diabetes, coronary artery disease, valvular disorder, endocrine disorder, and so on. It is critical to tackle all these coexisting conditions so that their malignant effects on the heart function can be checked or ameliorated.
Particularly important are those conditions related to structural defects of the heart such as valve narrowing or leaking, artery narrowing, which might need heart surgery or angioplasty, and these measures can be dramatically life-changing.
High blood cholesterol should also be treated because lowering cholesterol aggressively with statins has been shown in some cases to improve valve scarring (aortic stenosis), and improve some categories of heart failure, as well.
What about alternatives and supplements?
Unfortunately good research studies on these alternatives or supplements, which meet rigorous scientific scrutiny, are lacking. As required with all allopathic (scientific Western) medicine, we need far more stringent proof than simple testimonials from a handful of patients, to attest to the claims of benefits of any drug for any ailment.
Ubiquinone (coenzyme Q10) has been studied somewhat more than most others, and has been shown to improve some subset of dilated heart muscle disorders, but the doses required are high (150 to 300 mg daily or more) and its outcomes are still debated by many.
In late end-stage heart failure, some relief of symptoms have been reported but survival is not much enhanced. In the context of newer medicines available these days, it is uncertain whether this drug can add meaningfully to heart failure patients.
Chinese herbs are also bandied about as useful medicaments for strengthening the heart. However, little is known of their provable benefits. Gingko, American ginseng and Korean ginseng are used frequently by many Asians, but their real or measurable effects are unknown.
But because of their widespread use (and we have not had reports of serious untoward outcomes) they are possibly not too harmful when used moderately.
Their use together with modern medicines are often not revealed to doctors, thus, their additive and/or beneficial effects if any, will remain as of now a mystery.
Ephedra (Ma Huang), which contains an active ingredient – ephedrine, a heart stimulant – has been shown to be very dangerous and has been banned by many health authorities, worldwide.
Ephedra has been used widely as an additive stimulant to many herbal products, which often are unlabelled and/or hidden from view.
Extremely dangerous and rapid erratic heart rhythms have killed some people in the West, so these should not be used.
Preventing sudden dying with specialised pacing therapy
Patients with heart failure may die of gradually fading heart function and ultimately, pump failure.
However, a sizeable number die suddenly from chaotic heart rhythm disorders such as ventricular tachycardia (VT) or ventricular fibrillation (VF), or even pulseless atrial fibrillation (AF) or very slow heart rhythm.
Many research studies in recent years have shown that controlling these abnormal rhythms by applying an electric shock when these occur can be lifesaving. This has led to a new generation of special pacemaker-like internal defibrillators which not only can detect these VT or VF, but can also give out small shocks to terminate such dangerous rhythm disturbances.
Studies have now confirmed that using these so-called implantable cardioverter-defibrillators (ICDs) can save lives and actually prolong survival by as much as 30 to 40%!
Unfortunately these ICDs are very expensive and are only now being recognised as a useful addition to our therapeutic arsenal to combat unexpected deaths in heart failure patients.
One more new device which has come into the field of treating end-stage heart failure is another pacemaker-like device which helps synchronise the two sides of the heart chambers, so that its pump capacity can be better coordinated.
This is the CRT (cardiac resynchronisation therapy) and the technique was earlier called biventricular pacing, because it requires pacing both sides of the right and left heart pumping chambers, in a carefully timed sequence.
This device is only useful in those with very low pump capacity (ejection fraction of less than 30%) and with delayed electrical activation of the heart muscle, a term called cardiac dysynchrony.
This can be picked up using the simple resting ECG. This would show up as a widened contraction component (wide QRS) of the heart rhythm complex.
Again this is another very expensive therapeutic option which requires skilled and experienced hands, of which there are only a few in Malaysia. But in the US, the numbers have risen exponentially in the recent five to six years.
Heart transplant – a last gasp resort
Ultimately the most definitive therapeutic option for the failing heart is that of heart transplantation.
However, in view of this extremely precious yet life-changing option, only those with end-stage or refractory heart failure can qualify. Not only are donor hearts rare, but their careful matching to the potential recipient makes it also a dicey affair.
Clearly only those who have undergone repeated hospitalisation, receive repeated doses of toxic but necessary heart stimulant intravenous treatment, have very low effort capacity, survived repeated dangerous life-threatening heart rhythms, would meet the stringent requirements to be accepted into most heart transplant programmes.
Beside these, patients must be relatively young (usually less than 50 years), have no associated diabetes or kidney disorder, cancers or other serious infectious tendencies.
In most centres these days, the survival rate after heart transplant is quite excellent. More than 85% would survive the first year, and 60% for five years, in well selected patients. Of course these patients would have to take anti-rejection drugs for life, but at least it is a life each of them can still claim to have.
See your doctor
When you have worries about whether you might have heart disease or heart failure, please consult your doctor. No amount of reading will be enough, and may delay proper treatment!
The members of the panel include: Datuk Prof Dr Tan Hui Meng, consultant urologist; Dr Yap Piang Kian, consultant endocrinologist; Dr Azhari Rosman, consultant cardiologist; A/Prof Dr Philip Poi, consultant geriatrician; Dr Hew Fen Lee, consultant endocrinologist; Prof Dr Low Wah Yun, psychologist; Dr Nor Ashikin Mokhtar, consultant obstetrician and gynaecologist; Dr Lee Moon Keen, consultant neurologist; Dr Ting Hoon Chin, consultant dermatologist; Assoc Prof Khoo Ee Ming, primary care physician. For more information, e-mail starhealth@thestar.com.my
The Star Health & Ageing Advisory Panel provides this information for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care.
The Star Health & Ageing Advisory Panel disclaims any and all liability for injury or other damages that could result from use of the information obtained from this article.
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