Preventing CHF and CHD with ultrasound

With pathological knowledge and the cost of healthcare increasing, preventative medicine is becoming central to healthcare policy in the developed world. Many of the risk factors and stages of disease progression are now well understood, so identifying these early warning signs in patients allows treatment to start earlier and stop disease progression sooner, potentially saving millions of pounds in healthcare expenditure and increasing life expectancies. Coronary heart disease (CHD) is a modern condition that is becoming more common and is a risk factor in itself for a number of conditions such as strokes, heart attacks and kidney failure, making early detection of any arterial disease important. GPs tend to favour traditional techniques such as testing a patients’ blood pressure to check for the early warning signs of coronary heart disease for ‘at risk patients’ (smokers, high blood pressure, high cholesterol, diabetics and the obese). However, the problem with such techniques is that they only enable the clinician to see what is happening externally and does not necessarily expose pre-clinical risk factors acting on the heart itself. In many cases, coronary heart disease does not present itself until the patient suffers an acute incident such as angina or a heart attack. Indeed, many cardiologists now acknowledge that in most cases CHD and congestive heart failure (CHF) are caused by a blockage in the coronary arteries. Atherosclerosis is the cause of blocked arteries – coronary artery disease (CAD) – and is a symmetrical process that occurs gradually over many decades. It occurs when deposits of calcium, fats and abnormal inflammatory cells attach themselves to the walls of the arteries forming blockages or plaques. This, in turn, makes the vessel narrower, hardened and stiff, which leads to an increased blood pressure. In the event that a plaque ruptures, a blood clot may form within the artery, completely blocking blood flow, which can cause a heart attack. Most diagnoses tend to look for larger blockages within the coronary arteries. However, in many cases, the plaque that eventually ruptures would have been considered non-significant prior to the event itself. It is, therefore, important to find any evidence of CAD as plaque rupture is potentially life threatening.

Diagnosing disease

Before ultrasound was used to provide an imaging solution, diagnoses of vascular disease was made by an angiogram – an intravenous injection of contrast medium followed by an Xray or MRI to see how open the blood vessels are. More recently, coronary calcium scans (a form of CT) have been used to detect the presence of calcium, and by proxy, the amount of plaque. However, even this method is unable to detect stresses on the heart at the time, as it is effectively measuring volume rather than pressure. Since its introduction in the early 1950s, ultrasound has existed in the guise of the echocardiograph which is an invaluable tool for cardiologists. However, the use of ultrasound in cardiovascular medicine is no longer limited to basic imaging of the heart’s structure as a whole. In the last few years, clinical attention and diagnosis has shifted towards measuring specific internal risks, namely arterial elasticity or stiffness.1,2 There are three factors driving this new diagnostic approach. Firstly, eminently workable, non-invasive measurement methods have become available (tonometric, sonographic and oscillometric methods) which make a reliable pulse wave analysis possible.2 Secondly, pathophysiological knowledge has significantly increased. For example, the rise in easily measurable pulse wave velocity as a function of increased arterial stiffness – which occurs due to loss of elastin and collagen build-up3 and tends to be irreversible. And finally, it is also possible to assess the augmentation index caused by a superimposition (augmentation) of the antegrade aortal blood flow. This central aortal pressure, determinable by the above mentioned measuring methods, records the pathophysiologically important internal blood pressure situation in a more valid and reliable manner than peripheral measurements like Riva Rocci apparatus.1 Furthermore, pharmacotherapeutic studies for treating arterial hypertension have shown that centrally recorded (and then reduced) arterial pressure leads to more reliable blood pressure stabilisation, with a reduction in cardiac event rates (ASCOT study,4 CAFÉ subgroup analysis5). An additional study, involving 11,506 hypertensive patients, even managed to confirm that this correlated to a decrease in mortality.6