Analysing waves in blood to understand heart disease

Wave intensity analysis (WIA) is a technique that allows researchers to analyse the waves travelling within the cardiovascular system that govern blood flow. A recent review published in the journal Global Cardiology Science & Practice highlighted some applications of WIA for developing more detailed understandings of some heart conditions, such as heart failure¹. The technique, the researchers say, has proven to be highly sensitive and is emerging as a powerful tool to investigate the blood vessels that feed the heart’s muscle.

Scientists using WIA have found that six waves move through the arteries that feed the heart’s muscle, the coronary arteries, in a single contraction–relaxation cycle. One of these waves, called the backward decompression wave (BDW), is particularly relevant to understanding some cardiac diseases.

The BDW is the energy wave traveling within the coronary arteries that originates from the microscopic blood vessels of the heart as the cardiac muscle relaxes at the end of a cardiac cycle. This relaxation leads to the re-expansion of the blood vessels running through the heart muscle, called the myocardium, which facilitates this decompression wave. The BDW can provide useful information about the health of the myocardium and the efficiency of its blood supply.

For example, when the wall of the heart’s left pumping chamber becomes thickened, a condition called left ventricular hypertrophy, the myocardium fails to relax properly, leading to a weak BDW. WIA is being used to gain further insight into this condition and could prove useful in assessing how patients respond to treatment.

The aorta is the main artery that provides the body with oxygenated blood. When the valve that separates the aorta from the left ventricle abnormally narrows, in a condition called aortic stenosis, the heart must contract harder to push blood through it. This also means it relaxes more afterwards, causing a dramatic increase in the BDW. This is swiftly reversed when the condition is treated. WIA could thus be used for further investigations into the effects of aortic stenosis and its treatment.

“Until recently, WIA was a solely invasive tool that necessitated the use of intracoronary wires,” says Christopher Broyd from Imperial College London.

This involved inserting a wire through the neck into the main artery that feeds the heart muscle and obtaining a 30-second-long measurement of the blood flow. He and his team, however, have recently developed a novel non-invasive method that measures coronary flow using a conventional echocardiogram and a special blood pressure cuff.

“As the technology becomes more applicable with this non-invasive approach we envisage it moving into the clinical arena … to assess response to therapy or disease progression,” he says.

1. Broyd, C. J., Davies, J. E., Escaned, J. E., Hughes, A. & Parker, K. Wave intensity analysis and its application to the coronary circulation. Glob. Cardiol. Sci. Pract.2015, 64 (2015). | article