Dr Carl Shakespeare consultant cardiologist  
       
 
   
consultant cardiologist
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Conducting System

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Murmurs of the Heart

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Disease

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Angioplasty

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Cardiac Medication:

Beta Blockers

Calcium Antagonists
Nitrates
ACE Inhibitors
Angiotensin Receptor Blockers
Diuretics
Antiarrhythmic Drugs
Blood Thining / Anticoagulation

Beta Blockers
This includes a group of drugs usually ending in “-ol”, such as atenolol, metoprolol, nebivolol, carvedilol, and bisoprolol. This group of drugs acts primarily by reducing heart rate and the strength of heart contraction. The major use of these drugs was in treating hypertension (previously)and angina. Recent concerns about the greater likelihood of developing diabetes have limited its use now. Certainly beta blockers are no longer first line treatments for hypertension. The difficulty is in patients who have been on beta blockers for some time. If blood pressure is still not optimally controlled, then it would be an opportunity to stop the beta blocker and consider alternatives. For those patients who have been on a beta blocker for some time and have good blood pressure control, then current recommendations are that they remain on the beta blockers.

For angina, beta blockers are the mainstay of treatment because they reduce the demands or work the heart has to do. In addition, for patients that have had a heart attack, long term use of beta blockers will protect the heart against adverse events.

 

Beta blockers are also used in arrhythmias such as atrial fibrillation, atrial flutter and other SVTs. More recently, beta blockers have been used to treat heart failure. In this case the medication may not necessarily improve symptoms of breathlessness for at least a month. Indeed some patients could feel worse for that time, but as long as the patient can tolerate it, breathlessness and prognosis will improve.

Side effects include fatigue and shortness of breath, especially at first. These symptoms usually improve after a week or two. For patients with asthma, these drugs are relatively contraindicated. Quite commonly these drugs cause sleep disturbances, vivid dreams, and occasionally nightmares. For patients with peripheral vascular disease, leg pains can become worse. For patients in whom lowering heart rate is important to treat angina, but cannot tolerate beta blockers, a new drug called procoralan may be an alternative.

Calcium Antagonists
Includes drugs such as amlodipine, nifedipine, felodipine, lercandipine, diltiazem and verapamil. They have little to do with calcium in bones! This class of drugs acts to dilate blood vessels. This would have applications in treating angina by dilating the coronary arteries to improve the blood supply to heart muscle, or in hypertension by dilating larger blood vessels to reduce the pressure. The drugs can be classified as having or not having heart rate lowering properties. Both diltiazem and verapamil have heart rate lowering abilities and would be especially applicable in hypertensive and anginal patients with higher heart rates.

Nicorandil is another type of blood vessel dilating drug that acts in a slightly different way, and thus can be added to other calcium antagonists to treat angina.

As these drugs dilate blood vessels (especially nifedipine and amlodipine), they can cause headaches, flushing of the skin, and ankle swelling. The latter needs to be distinguished from the reduced heart muscle function effects (more so with verapamil and diltiazem)) that can also cause swelling.

The heart rate lowering effects can be used to treat some of the arrhythmias such as atrial fibrillation, atrial flutter and SVT. back to index

Nitrates
Includes drugs such as GTN spray, and isosorbide mononitrate. This class of drugs dilates blood vessels directly which can be used to treat angina by dilating coronary arteries. As with the calcium antagonists, the main side effects include flushing and ankle swelling. These drugs are usually prescribed as “add ons”, to relieve residual anginal symptoms after beta blockers and calcium antagonists.back to index

ACE Inhibitors
These are drugs ending in “-pril”, such as lisinopril, perindopril, ramipril, enalapril, and trandolopril. “ACE” stands for Angiotensin Converting Enzyme. By inhibiting the enzyme, blood vessels dilate, and this effect can be used to treat hypertension. With a reduced blood pressure, or more specifically lower resistance within the circulation, the heart needs to perform less work to pump blood. This is the major application in heart failure where these drugs are used, and result in less strain on the heart and potentially better function. As with beta blockers they take about a month to improve symptoms of breathlessness.

Not quite related to the heart, but in diabetes, these drugs are very helpful in reducing potential kidney damage.
ACE inhibitors have few side effects, but the most troubling one is a dry cough. To find out whether the cough is related, try stopping the drug for a week and see whether the cough disappears.back to index

Angiotensin Receptor Blockers
These are “cousins” to the ACE inhibitors, acting on blood vessels in a slightly different way to reduce pressure and resistance. Drug names include Losartan, Candesartan, Irbesartan, and Valsartan. They are used especially when ACE inhibitors are not tolerated. As with ACE inhibitors they are used in hypertension and heart failure, and have even fewer side effects.back to index

Diurectics
These include bendrofluazide, frusemide, bumetinide and metolazone. These are commonly referred to as “water pills”. They do assist in removing extra fluid from the circulation. So in heart failure where excess fluid accumulates in the legs, and the lungs (causing breathlessness), diuretics will offload the excess. In hypertension, only bendrofluazide is used. Its action is less of a diuretic in this instance and more of a vessel dilating drug. Another diuretic subgroup includes spironolactone and eplerenone. They can be used in resistant hypertension and as an additive in resistant heart failure. The specific side effect of spironolactone is breast enlargement in the male.

The main side effect of diuretics is dehydration. This is more likely to occur in summer and in hot climates, and will affect the elderly more readily. Blood salt disturbances, particularly of potassium can occur with frusemide and bumetanide. This may cause mild arrhythmia, atrial fibrillation, and general fatigue. Spironolactone is more likely to cause a raised potassium that can adversely affect the heart.back to index

Antiarrhythmic Drugs
These include the beta blockers and calcium antagonists mentioned earlier. The list is exhaustive and may be classified according to either mechanism of action or site of action. Side effects include all those that can occur with any drug such as nausea, fatigue and bowel disturbances. The major concern is that despite treating rhythm disturbances, they can actually precipitate arrhythmia. Thus for any worsening of symptoms or new onset of palpitations or dizziness one should seek medical attention.

Digoxin: This is a common drug and is used to treat heart rate increases in atrial fibrillation. It is less effective in atrial flutter and intermittent episodes of fibrillation. In cases where palpitations are exercise related, the drug is less effective and needs to be bolstered with either a beta blocker or verapamil. Toxicity is increased with kidney disturbances and a low potassium. Patients on digoxin should have their blood chemistry monitored occasionally.

Flecainide and Propafenone: These two drugs are primarily used for supraventricular tachycardia (SVT). Thus can be used in atrial fibrillation, flutter, Wolf Parkinson White and Atrioventricular Nodal Reentrant Tachycardia (AVNRT). These drugs are contraindicated in the elderly, heart failure and in patients with ischaemic heart disease.

Sotolol: This is strictly speaking a beta blocker but also has other chemical actions. Primarily it is used to treat intermittent atrial fibrillation. It has in the past been used to treat ventricular arrhythmias.

Amiodarone: This is a very important drug that is used to treat both atrial and ventricular arrhythmias. It is very important to realise that this drug has long term toxicity and I very rarely use it beyond a year. The commonest side effect is photosensitivity, where the skin becomes sensitive to sunlight and burns easily. You can even get a suntan on a sunny winters day! Otherwise the main side effects include thyroid disturbances and lung damage. Anyone on a protracted course of amiodarone should have six monthly chest X-rays and thyroid checks. Thyroid disturbance include thyrotoxicosis where the thyroid becomes overactive: patients can become shaky irritable and lose weight. More importantly, an overactive thyroid can cause atrial fibrillation, so if the drug is being used to treat fibrillation in the first place, and symptoms worsen, then thyroid activity needs to be checked promptly. An underactive thyroid can also occur with prolonged amiodarone use. Symptoms include fatigue, lethargy and weight gain.

Amiodarone can be used to treat intermittent atrial fibrillation, but its long term use for this should be questioned. More commonly it can be used in preparation for electrical cardioversion. In this process the blood is thinned for 6 weeks with warfarin. The arrhythmia is electrically stabilized for at least 4 weeks then an electric shock is delivered with the patient anaesthetized to electrically convert the patient back to a normal rhythm (see under atrial fibrillation). After a period of time amiodarone should be stopped after a period of time. In cases where persistent atrial fibrillation remains despite having been treated with amiodarone, it is wise to replace it with another antiarrhythmic drug to avoid long term toxicity.
Amiodarone is sometimes used for treating ventricular arrhythmia. In asymptomatic short episodes it should not be used. In cases of more serious ventricular arrhythmia, especially if patients are symptomatic, or episodes are prolonged (> 30 sec), it can be considered. In the context of patients with a background of previous heart attacks or heart failure, then an ICD defibrillator would be better. However if an ICD is considered inappropriate, then amiodarone is an alternative.back to index

Blood Thining / Anticoagulation
In different circumstances it is considered worthwhile to thin the blood. Infact, the blood is not thinned at all – it’s just an expression. The process is to reduce the coagulability either in the arterial system such as the coronary arteries, or to prevent clot building up in the veins or heart chambers.

Aspirin: this drug reduces the stickiness of platelets that prevents clot building up within arteries such as the coronary arteries of the heart or the carotid arteries that take blood to the brain. This reduces the chance of clot building up and blocking the coronary artery causing a heart attack, or clot going to the brain to cause a stroke. Treatment is usually lifelong after a heart attack or a stent. The dose is usually 75 mg daily

Clopidogrel: This is another type of platelet drug that reduces lot build up. It can be used in place of aspirin if patients are intolerant. In patients with heart attacks or drug eluting stents, clopidogrel provides additional protection when added to aspirin. In such cases clopidogrel is used for at least a year. There is sometimes confusion when bare metal stents are employed instead of drug eluting stents. In such cases, only a month of clopidogrel is needed. Dose is usually 75 mg daily.

Warfarin: this type of anticoagulation works by acting on the coagulation profile rather than platelets. It is used to treat larger clots. Commonly used in patients with clots on the lung or thrombosis in the veins of the leg.  For patients with artificial mechanical heart valves, warfarin is maintained to prevent clot building up between the struts and jamming the valve. In addition it prevents bits of clot building up and then dislodging to cause a stroke.

In atrial fibrillation, clot can build up in a stagnant left atrium, and dislodge and cause a stroke. In patients due to have an electrical cardioversion, warfarin treatment for six-eight weeks dissolves clot such that when the electric shock is delivered, no clot would dislodge. In patients with permanent atrial fibrillation in whom electrical cardioversion is not indicated, long term or lifelong treatment with warfarin should be considered. Warfarin needs to be regulated by regular clotting checks in an anticoagulant clinic. When first initiated, a loading dose for three days is given, then the degree of clotting measured. After that the individual dosing requirements will vary from patient to patient and from time to time.back to index