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The effects of TrP activity developing in these two muscles will be discussed in detail when consider-ing abdominal pain in Chapter 20. It is necessary to state here, however, that TrP activity in the upper part of the rectus abdominis muscle and in the upper part of the external oblique muscle may

cause pain to be referred upwards over the lower part of the chest anteriorly. When this occurs, either on the left or right side, it is liable to be mis-diagnosed as being pleural in origin in spite of the absence of either a pleural rub or any signs of intrapulmonary disease. And on the left side it may closely mimic the pain of coronary heart disease (Kelly 1944).

Activation of TrPs

This commonly occurs either as a result of acute trauma or chronic overloading with the latter often having an occupational basis.

TrP examination

The patient should be placed in the supine posi-tion and instructed to stretch the muscles by hold-ing the breath in deep inspiration. TrPs in the upper part of the rectus abdominis are usually to be found in the angle between the costal margin and the xiphisternum. In the upper part of the external oblique muscles they are either along or under the lower border of the rib cage (Figs 20.3 and 20.4).

Deactivation of TrPs

Each TrP should be trapped between two fin-gers prior to inserting a needle into the tissues overlying it.

ANTERIOR CHEST WALL MTrP PAIN AND CARDIAC PAIN – THE DIFFERENTIAL DIAGNOSIS

As has already been stated, muscles in the chest wall when subjected to trauma of one kind or another may develop TrP activity with the pattern of pain referral resulting from this being identical with that seen in coronary heart disease. Also, the same chest wall muscles may develop satellite TrP activity as a result of being within the area affected by pain from coronary heart disease.

It is, therefore, easy to see that diagnostic confu-sion may readily occur and, whilst it is obviously important not to overlook angina when present, it

Figure 12.11 A, B and C The pattern of pain referral from a trigger point or points (▲) in the serratus anterior muscle.

B A

C

TP

is equally essential not to diagnose chest pain as being anginal when it is only muscular in origin.

This is a mistake as frequently made today as it was when Allison (1950) wrote in reference to non-cardiac chest pain:

… the frequency with which such patients are seen in routine out-patient work emphasizes the need for a reorientation towards pain in the chest, and suggests that in clinical teaching pride of place is too often given to angina pectoris in explanation of the pain, and too little regard is paid to local structural causes.

One particular circumstance when primary anterior chest wall TrP pain may be overlooked is when it occurs in someone known to have a his-tory of coronary heart disease. Chest pain arising soon after recovery from a myocardial infarction, if accompanied by fever and a pericardial rub, is readily recognized to be part of the post-infarction syndrome (Dressler 1959). If, however, it occurs by itself, there is a tendency to assume it must be anginal, and to overlook the possibility that it may have arisen as a result of the activation of TrPs. Similarly, anterior chest wall TrP pain may erroneously be assumed to be anginal when it occurs at some time following coronary by-pass surgery.

The relevance of all this to the practice of TrP acupuncture is that, whilst pain arising as a result of the primary activation of TrPs is readily allevi-ated by means of superficial dry needling carried out at these points, and whilst, as will be explained later, treatment of this type may have a limited place in the overall management of coronary heart disease, clearly before using it for the alleviation of any type of chest pain, it is essential to have made an exact diagnosis as to its cause. For this reason the various problems that arise in differentiating between cardiac pain and TrP pain will now be discussed.

When attempting to distinguish between these two types of pain careful history-taking is clearly of prime importance, but this by itself may be incon-clusive. This is because, whilst with ischaemic heart disease there is substernal tightness and frequently radiation of pain up into the neck, across the chest to the shoulder and down the left arm, what is less

well known is that pain emanating from TrPs in anterior chest wall muscles may have a referral pattern exactly the same as this. And, moreover, although angina is characteristically brought on by exertion, chest wall TrP pain may also be aggra-vated by this. The difference is that whereas with angina the amount of effort required to produce the pain is fairly constant, with TrP pain it is liable to vary widely from day to day. Also, pain of this type is often aggravated by stretching and twisting movements of the chest wall muscles.

Furthermore, angina may on occasion come on at rest. When this is due to the heart rate increas-ing in response to some emotional upset, it usually only lasts for a relatively brief period, whereas, in contrast to this, when TrP pain develops at rest it is liable to persist for a long time. Also, both types of pain may disturb sleep. With ischaemic heart dis-ease this is sometimes because of a tachycardia brought on by dreaming, and with non-cardiac TrP pain, it is due to the adoption of some posture that puts the muscles on the stretch.

The finding of TrPs on clinical examination is clearly only of limited value as it does not help to distinguish between cardiac pain with superim-posed TrP pain and primary myofascial TrP pain.

The response to a therapeutic trial of sublingual glyceryl trinitrate may also be misleading since the placebo effect of this ensures that up to 30% of patients with chest pain from any cause may be improved.

Electrocardiography, too, has its limitations, as it is not uncommon for a patient with wide-spread coronary heart disease to have a normal tracing. Conversely, any abnormal changes seen may only be a reflection of what has happened in the past and have no relevance to the pain under investigation. An ECG taken after exercise testing may also occasionally be misleading.

It therefore follows that there are times when in order to distinguish between coronary artery disease pain and a non-cardiac chest wall pain such as that which emanates from primarily activated TrPs either a coronary arteriogram, or assessment of left-ventricular function by the more recently introduced technique of radionu-clide technetium angiography performed at rest and during exercise (Borer et al 1977, Petch 1986) may be necessary.

THE USE OF TRADITIONAL CHINESE AND TrP ACUPUNCTURE IN THE TREATMENT OF CORONARY HEART DISEASE

Angina

The use of traditional Chinese acupuncture for the treatment of angina has, over the years, been extensively investigated by Ballegaard and his co-workers (Ballegaard 1998). Nevertheless, in view of the various highly effective anti-anginal agents now available, the place for this in its routine man-agement must be strictly limited.

If, however, superimposed upon episodes of anginal pain, a more persistent type of pain devel-ops with tenderness of the chest wall, then TrPs should be sought and, if found, should be deacti-vated by means of the carrying out of superficial dry needling at these TrP sites.