Shortness of breath is a very common symptom and is primarily caused by problems in the lungs or the heart. Some causes of shortness of breath can be serious. Therefore, breathlessness should always be taken seriously and investigated comprehensively.
Cardiac Causes of Shortness of Breath
A range of problems in the heart can result in breathlessness.
Heart failure is a collective term used to describe a condition where the heart can no longer pump blood around the body effectively. Heart failure can be the end result of myocardial infarction (heart attack) or a cardiomyopathy (a disease of the heart muscle which can result in stretching or stiffening of the heart muscle that interferes with the normal function pumping of the heart).
Shortness of breath associated with heart failure starts slowly, and progressively worsens over a period of days, or sometimes weeks. Patients often complain of breathlessness during activity which settles with rest. Most patients also develop swelling of the ankles and breathlessness when lying flat (especially at night) – a phenomenon known as orthopnea. In the worst cases of heart failure breathlessness can occur at rest.
The screening tests for diagnosis of heart failure can be done on an outpatient basis, and include an ECG (heart trace) and echocardiogram (ultrasound scan of the heart). However, more sophisticated tests are also often required to identify the underlying cause such a coronary angiogram or MRI scan of the heart.
Tablets are the mainstay of treatment for heart failure. These include diuretics (water tablets) to get rid of excess fluid accumulation in the body, ACE inhibitors which reduce the blood pressure and beta-blockers that reduce the cardiac workload by slowing rate and force with which the heart beats. If heart failure is caused because of a blocked coronary artery, for example after a heart attack, the artery will need to be unblocked using angioplasty. In extreme cases of heart failure complex pacemakers may be of value to help the heart with its remaining function. These are often referred to as bi-ventricular pacemakers.
Heart rhythm abnormalities
An abnormal fast or slow heart rate can compromise the normal pumping function of the heart and result in shortness of breath.
Common causes of an abnormal fast heart rate include atrial fibrillation (AF – an irregular and fast heart rhythm) or supraventricular tachycardia (SVT – a regular and fast heart rate). Conversely, a very slow heart as a result of heart block can also have the same effect.
However, it is unlikely that heart rhythm abnormalities present with breathlessness alone. In the context AF and SVT most patients will also experience concurrent palpitations and dizziness. Patients with heart block suffer from dizziness, lack of energy, and in serious cases may lose consciousness (faint).
Both fast and slow heart rates are eminently diagnosed with an ECG (heart rate) and require immediate treatment. If AF and SVT are associated with severe symptoms the main treatment is to re-synchronise the heart with a small electric shock that is delivered through paddles on the chest wall (a process called cardiovesrion). Cardiovesrion is performed under sedation as it can be painful. Alternatively, tablets such beta-blockers or digoxin can be used to control the heart rate. If there is no reversible cause for heart block (such as an overdose of tablets that slow the heart rate) most patients will need a pacemaker.
Once normal heart rhythm has been restored further tests need to be done to identify the cause for the abnormal heart rhythm. These include simple blood tests (to look for abnormalities in the levels of electrolytes such as potassium), echocardiogram (to assess the size and pumping function of the heart), MRI scan of the heart (to assess whether there is disease in the heart muscle) and occasionally an angiogram if coronary artery disease is suspected.
Myocardial infarction (heart attack)
A myocardial infarction can rarely be “silent” in that it is not associated with chest pain. This group of patients often develop sudden onset breathlessness. Silent myocardial infarcts are more common in patients who have diabetes or the elderly.
As outlined in the section on chest pain an ECG is often sufficient in making a diagnosis. The heart attack must be treated as a matter of emergency to prevent damage to the heart muscle.
Causes of shortness of breath secondary to the lungs and airways
There are a number of important causes of breathlessness that arise from the lungs or airways (pulmonary breathlessness). As for cardiac causes of breathlessness these conditions need to be diagnosed and treated rapidly.
Asthma and obstructive airways disease (alternatively known as emphysema or COPD) that arise secondary to “spasm” in the airways are the most common cause of pulmonary breathlessness in the UK. Patients suffering these conditions often have an accompanying wheeze. Alternatively, a chest infection leading to bronchitis or pneumonia can also cause breathlessness. Pneumonia is often accompanied by fever and a sharp or stabbing chest pain. Other less common pulmonary causes of breathlessness are a pneumothorax (when a lung collapses), pulmonary fibrosis (a condition that leads to thickening of the lung tissues), or pulmonary embolism (blockage of blood vessels in the lung with blood clots).
Finally, shortness of breath could be the result of conditions unrelated to the heart or lungs. For example, severe anaemia and panic attacks may manifest with breathlessness.