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Dr Malik explains the anatomy of the heart

Please see the below PDF that was created by Edwards Life Sciences as a free resource. Dr Malik works at Hammersmith Hospital London, and is a senior interventional cardiologist. He also works at OneWelbeck Heart Health, the largest private cardiology practice in London, and is the Medical Director.

Heart Anatomy Guide

Basics of the heart

The heart is a pump. Imagine a washing machine- It needs electricity- so does the heart (it has a built in electrical system). It needs a water supply –so does the heart (blood in this base). It needs the drum working –so does the heart (those are the heart chambers). To work properly, and beat 70-80 times per minute, al needs to be order- the heart lasts longer than any washing machine!


The chambers of the heart

The heart has 4 chambers.

The ones on the right side collect blood from the body and brain (the right atrium) and the  push it to the lungs (the right ventricle). This is a low pressure system. It only need to get to the lungs- they are close by. The pressure needed is about 30mmHg. The right ventricle 9s crescent shaped and wraps around the left ventricle.

The ones on the left collect blood from the lungs (the left atrium) and push it all over the body and brain (the left ventricle). The left ventricle is thus the most important chamber. It is bigger and stronger than the right ventricle and needs to generate 100-120 mmHg pressure to allow blood to pump to your brain when you are standing up. The left ventricle is like an ice-cream cone, with the right ventricle like your hand wrapped around it.


The electricity and pacing system in the heart

The heart has a built in pacemaker- it lives in the top of the right atrium. It is called the sino-atrial node (SA node).  It fires of at about 70 beats a minute until it needs to beat faster- when it can accelerate to over 180 if needed. It sends electricity around the atria making them contract.

It also fires off the secondary pacemaker – The atrio-ventricular node (AV node). It sits in the model of the heart. That is clever in that there is a built in delay- so that the atria have time to empty into the ventricles before they contract.

The AV node has “bundles” of cables that go to the left and right ventricles, again clever as then that means that the contraction of the ventricles occurs from the  apex of the “ice-cream cone”, so that efficiency is maximised.


The valves

Blood should only flow one way, just as water in the washing machine should only flow one way. The heart has 4 valves to help the 2 ventricles pump.

Right side- Inflow: tricuspid valve, outflow: pulmonary valve

Left side- Inflow: mitral valve, outflow : aortic valve

Problems with the right sided valves are tolerated better than left sided as the right is a low pressure system.

Valves can leak or narrow- just as in your washing machine.


Disease of the heart


  1. Too slow (bradycardia)- the pacemaker is failing and a new pacemaker may be needed
  2. Too fast (tachycardia)- there are other parts of the heart that accelerate the heart way above normal- this could be ventricular tachycardia (from the ventricle) or supra-ventricular tachycardia (above the ventricle). Treatment may be medication or cutting the short –circuit (ablation)
  3. Atrial fibrillation (AF)- that is usually tool fast a beat, but can also go too slow. Treatment is with medication or ablation.

Muscle disease (cardiomyopathy)

There are many types of these- affecting the ventricles- some with weakened and stretched (Dilated cardiomyopathy), some too chunky and thus not working well (hypertrophic cardiomyopathy). These will need specialist diagnosis and treatment.

Valve disease

The main ones in adults are:

  1. Aortic stenosis- the aortic valve is severely narrowed (stenosis) and you have chest pain, breathlessness or dizzy spells, seek urgent attention. Severe symptomatic aortic stenosis (SSAS) has a 4% per month death rate.
    1. Treatment can be with surgery or transcatheter aortic valve intervention  (TAVI or TAVR). Dr Malik is an expert in TAVI and run the Imperial College Healthcare NHS Trust program.
  2. Aortic regurgitation-the aortic valve is leaking, and this puts a strain on the left ventricle.
    1. Treatment can be with medication, with open heart surgery or with TAVI
  3. Mitral stenosis- the mitral valve is thickened and narrowed. this is mainly due to rheumatic heart disease, and thus is less common in western countries.
    1. Treatment is with medication, surgery, or balloon stretching- which in younger patient may avoid open heart surgery
  4. Mitral regurgitation- leaking mitral valve. This can be due to problems with the leaflets or problems with the ring the leaflets are on- if the ring stretches, then the leaflets don’t meet and the valve leaks.

Coronary disease:

Blood gets to the heart via coronary arteries. If these get narrowed, then the heart muscle is starved of oxygen and glucose. It cant work. This can happen slowly or suddenly

  1. Sudden blockage- a heart attack, or myocardial infarction (MI). Treatment is urgently needed. Muscle is dying every minute there is a delay. You should get to hospital and the cardiologist will try to open the blood vessel with an angioplasty and stent (known as PTCA or PCI). Dr Malik has treated 1000’s of heart attacks in the last 20 years.
  2. Slow progression- angina is caused by progressive narrowing. The heart can cope better with this, but it can lead to chest pain on exertion, breathlessness, or tiredness. Treatment may me medication, a PCI or Coronary artery bypass surgery (CABG). You will need tests and probably a coronary angiogram to decide the best treatment for you.

In this brief overview of the heart and its functions, Dr Malik has tried to cover some of the more common problems. What is clear is that the heart is an amazing organ. Look after it and it will keep going for nearly 100 years. As proven by Prince Phillip in March 2021.

Complex PFO closure with Dr Iqbal Malik

Dr Malik does a live PFO closure. A PFO or patent Foramen Ovale, is a flap in the heart that is needed in the womb, but serves no purpose in the adult. It can in rare cases be associated with stroke. Closing the PFO with an umbrella device leads to a much reduced chance of recurrent stroke. Dr Malik is a leading expert in the procedure, and as in this video, often demonstrates his techniques to other physicians. He works in London at Hammersmith Hospital, and OneWelbeck Heart Health.

Paravalvar Leak closure by Dr Malik

Dr Malik does a live Paravalvar leak (PVL)  closure- see the video of this highly complex case. The patient was very symptomatic with a huge hole in the centre of his heart, as a result of some sutures giving way a few months after lifesaving open heart surgery. He was now classed as inoperable by the surgeons who saved him the 1st time he was sick, Dr Malik put some “plugs” in and our patient has gone back to work!  This type of operation is done by a handful of operators in the UK- Dr Malik demonstrated this at a recent International meeting- the EST 2021 session on 13th February 2021. He works in London at Hammersmith Hospital, and OneWelbeck Heart Health.

Why we aim for tight blood pressure control in patients with hypertension

Blood pressure tends to increase as we get older and by the age of 60 about half of the population in the UK will have high blood pressure. For many this will start at a much earlier age.

This is really important because for every 12mmHg increase in systolic blood pressure (the top value) or every 5mmHg increase in the diastolic blood pressure (the lower value), the chance of having a stroke is increased by 40% and the chance of having a heart attack is increased by 25%. High blood pressure is often silent, causing no symptoms, so patients don’t know that they have it. That’s why we should regularly check our blood pressure so we can detect if it starts to go up early.

The picture shows that the higher the blood pressure, diastolic or systolic, the higher the risk of stroke. There is a similar relationship with blood pressure and the risk of heart attacks.

The risk of getting high blood pressure or diabetes is very high in our White European (Caucasian) patients. However, it is more than twice as common in our South Asian, and four times as common in our African-Caribbean, patients. For diabetes, the risk in South Asians is four fold and in African-Caribbean patients, three fold.

A huge amount of research has been done on the treatment of hypertension and several studies have shown that for every 5mmHg reduction in diastolic blood pressure, the stroke risk is reduced by about 40% and the heart attack risk by about 15%. For systolic blood pressure every 12mmHg reduction in systolic blood pressure leads to the similar reductions in risk.

It’s because there is such a big benefit from treatment that we are so keen to measure blood pressure and if raised, to treat it very well.

There is some controversy about how low we go when we treat high blood pressure and there are differences between the UK, European and USA guidelines. There is recent evidence that getting the blood pressure to lower levels than we previously aimed for gives even greater protection from heart attacks and strokes. For many patients with hypertension a target blood pressure of 130/80mmHg or lower will be their optimal target blood pressure.

Good blood pressure control can be achieved with exercise, weight loss, reducing alcohol intake and dietary changes in some patients, though others may need medication. It’s important to assess patients individually and advise what the best blood pressure target is for them; one size doesn’t fit all.


Watch out for the iPhone 12 – Dr Malik Explains

Dr Malik says:

Watch out for the iPhone 12. It has a circular magnet that might deactivate your implantable defibrillator.

This article says it can happen- if the phone is over the device- which is usually under the skin by our left shoulder.

Some FitBits and other devices have been described to do the same.

If you have a pacemaker or ICD, consult your Cardiologist before buying the latest – or at least keep the thing well away from your chest!

Why do patients have side effects with statins?

In the UK, as in other westernised nations, we have extremely high cholesterol levels. This is unnatural and is a key reason for the very high levels of heart attacks, strokes and other cardiovascular problems that we have in our society. The average cholesterol is about 5mmol/l in the UK compared with under 2mmol/l in societies that don’t have westernised lifestyles. That means that even the average person has about two and a half times as much fat in his or her blood vessels every second of every minute of every day of their adult lives. It’s not surprising our arteries get clogged up with fat.

Altering our diet can have some impact on the cholesterol levels but it’s often only a small impact. We do have medications though that are highly effective at lowering cholesterol, in particular statins. These drugs have been tested in the best type of clinical trials. These are called double blind, randomised controlled trials, where patients either get the drug or a dummy (placebo) tablet. Neither the patient, nor their doctor, know which they have been allocated (randomised to). Then someone independent, who has nothing to do with any of the patients’ medical care, counts up how many deaths, heart attacks, strokes and other events occur in patients taking the statin drug and how many in patients taking the placebo tablets. Our department at Imperial College London ran and published one of these trials, the ASCOT study, assessing statins in patients with high blood pressure. This study others have shown that for every 1mmol/l reduction in LDL cholesterol there is about a 20% reduction in deaths, heart attacks or strokes in patients taking statins. In view of this key information from these studies, many patients are advised to take statins to reduce their future risk of heart attack, strokes and death. 

However, many patients remain sceptical because there is a lot of information about potential problems with statins in the press and on the internet. Some patients don’t like taking tablets because it is unnatural. Sadly though, much of our westernised life is unnatural, from breathing in the polluted air in our cities, to eating processed food, to taking insufficient exercise. That’s without some of the other potentially more damaging lifestyle choices we may make. Perhaps adding a tablet to what we eat that rebalances some of the adverse effects of Westernisation isn’t so bad in comparison.

A lot of patients describe side effects when they take statins and that can be an important reason that patients don’t continue with them. However many of the potential side effects like muscle aches or indigestion are vague, and people who don’t take stains also commonly get these symptoms. Statins have attracted a lot of media interest, probably because so many people are taking them, and there is a lot of public information about what the side effects might be. Concern about these possible side effects does influence some patient’s decision about whether or not to take statins. 

Our research team at Imperial College London recently looked back at side effect data in our ASCOT statin study. During the study there was very little difference in side effects in the patient group taking the statin compared with the group taking the placebo (the dummy tablet) when the patients didn’t know what they were taking. When the study was over and patients were told what tablets they were taking the reported side effects from the patients taking statins was much higher than when they didn’t know they were taking the drug.

Another study that has recently been published from our department at Imperial College London used an interesting technique where patients were either given a statin, a dummy tablet or no tablet at all for a period of time. They then switched to the other tablet or to no tablet so they had some time in each group.  They reported their symptoms during the course of the study. The study suggested that most side effects attributed to statins are because patients expect to get the side effects (called the “nocebo effect”). This is the reverse of the “placebo effect” that you may have heard of where patient’s feel better with treatments because they expect to do so. 

It’s important that when any treatment is recommended, there is a careful explanation of the benefits of the treatment and also a discussion about possible complications, side effects and how side effects may occur, along with other possible causes of those symptoms. This is particularly important with statins because all of the different information and opinions available on the internet and elsewhere, make it very difficult for patients to make the best choice for them. Our role as cardiovascular experts is to help patients make informed choices about what they wish to do. 


Wood FA, Howard JP, Francis DP et al. New Engl J Med 2020.