What’s A Cardiologist Doing Here?

  • A number of neurological conditions can be caused by something abnormal happening in the heart

  • Some symptoms, for example, faints and blackouts, and sometimes even fits and convulsions, can be caused by either an issue with the heart or within the brain, and so cardiologists and neurologists often need to work together to reach a diagnosis

  • Cardiological help is needed to perform and report cardiac investigations, and also to see, assess and treat patients when significant abnormalities are discovered.

Neurological Problems Caused by the Heart

These are basically of three types:

 

1. Blood Clots

Tiny blood clots (thrombi) can form in the heart under certain circumstances and can break off and be ejected into the arterial blood circulation where they can lodge into the circulation of the brain (and rarely nerve fibres elsewhere) and are known as emboli. The local blood vessels become blocked, either transiently or permanently, causing transient ischaemic attacks (mini-strokes) or strokes. These clots most commonly occur in three situations:

 

  1. A heart rhythm abnormality called atrial fibrillation (AF) or sometimes atrial flutter or tachycardia. In this rhythm, the upper chambers of the heart (the atrial) beat so rapidly and irregularly that they are ineffective in pumping blood properly into the main chambers, the ventricles. Although the heartbeat usually remains strong, blood in the atria can “pool”, and tiny clots form and can break off causing emboli.

    This ECG strip during persistent AF shows an irregular rhythm with an uneven baseline showing the fibrillatory waves:

 

 

This ECG shows 5 cycles of normal sinus rhythm (SR - the heart’s normal rhythm) followed by a short burst of AF and then a cycle of SR:

 

 

These rhythms can be diagnosed on a standard ECG, or on a monitor that can be worn, typically for 24 or 48hrs but now also for one or two weeks (see below).

 

 

  1. Patients who have had a large heart attack or have a damaged left ventricle (LV) for other reasons. In these patients, small or large clots can develop particularly at the “apex” of the left ventricle – parts of these can break off and block arteries in the brain or elsewhere. They are typically found on an ultrasound test of the heart – an echocardiogram as shown here:

 

 

In the past, valve problems such as rheumatic mitral stenosis were a major cause of blood clots, especially with AF, but this diagnosis is almost unknown in the Western world now.

 

 

  1. Prior to birth, with the foetus in the womb, there is a small flap in the atrial septum, which is the dividing wall between the left atrium (normally receiving oxygenated blood from the lungs once born) and the right atrium, receiving blood from the rest of the body via the veins. In utero, this allows oxygenated blood from the placenta to reach the left side of the heart and it is called the foramen ovale. In about 10% of the population, this does not close properly – persistent foramen ovale or PFO. Tiny blood clots are not rare in the venous system but are usually filtered out by the lungs and dissolve doing no harm. However, if they cross a gap in the septum, they can travel to the brain causing a stroke or mini-stroke:

     

 

Diagnosis is again with an echocardiogram, usually with a little injection into a vein of some agitated saline (or similar solution) when the micro-bubbles produced can be seen travelling across the septum. A variation of PFO is when the septum is closed at the site of the fossa ovale, but the “fossa” bulges – atrial septal aneurysm. Clots can form within this sometimes and then break off and cause damage.

 

 

2. Abnormal Heart Rhythms (Arrhythmias)

A variety of heart rhythms can cause a lack of blood flow causing dizzy turns or blackouts. These include very slow and very fast heart rhythms. Occasionally these arrhythmias can even lead to a fit (convulsion).

 

 

  1. Slow rhythms can occur if the “pacemaker” of the heart rhythm, the sinus node, discharges slowly or stops (sinus bradycardia or sinus arrest):

 

 

They can also occur when there is heart block, when the “P waves”, representing atrial contraction, arrowed below, do not conduct to the “QRS complexes”, representing the ventricles *the main pumping chambers), shown with the asterisks below:

 

 

 

  1. Fast rhythms, such as this run of ventricular tachycardia, can also cause a loss of cardiac output causing dizziness or collapse:

 

 

 

Arrhythmia Diagnosis

 

These arrhythmias can be diagnosed on a standard 12 lead ECG, if occurring all or most of the time.

 

Many occur only episodically and need some sort of long term monitor. These range from a 24-hour “Holter” monitor, which is attached to the chest via sticky electrodes and the recording made on a memory card which is later semi-automatically analysed:

 

 

More recently, 7 or 14 day devices have been developed, which are completely disposable and more discrete to wear, and the analysis is often more automated:

 

 

Finally, if the rhythm disturbance or suspected neurological event is very infrequent, a simple implantable device can be “injected” under the skin, which can detect abnormal rhythm events for up to three years. This is called an Implantable Event Recorder and has become a very powerful tool in many patients:

 

 

 

3. Obstruction to Blood Flow and Other Problems

Occasionally, neurological problems such as faints or dizzy turns can be caused by an obstruction to blood leaving the left ventricle. This is most commonly caused by a narrowed aortic valve:

 


It can also be caused by the heart muscle under the aortic valve getting too thick, obstructing the valve, seen in a variety of conditions, especially hypertrophic obstructive cardiomyopathy, usually known as HOCM.

 

Rarer causes of mechanical problems in the heart that can cause stroke include mitral valve prolapse (usually not a major issue) as well as an infection of the heart known as endocarditis and a rare tumour (usually benign) called an atrial myxoma – embolism of these can certainly occur, causing stroke.

 

These mechanical issues are all diagnosed by echocardiography and sometimes other more advanced scans such as CT scans and MRI.

The investigations listed above are available from NeuroHealthCare@CMC.

 

Dr Anthony Nathan is available for consultation and advice about all of these issues and can be contacted on 020 8420 4471