Abstract
Introduction
Cardiac ischaemia may occasionally present with only its referred pain at various locations. The typical referred pain radiates downwards to the left upper extremity and upwards to the jaw as its upper limit. However, some reports have presented unusual sites of the referred pain such as the tip of the nose, the tip of the tongue, bregma, occiput or mastoid (1). The exertional headache has been classified as a benign headache disorder, when no specific causes are found, by the International Headache Society (IHS) (2). It is very uncommon for myocardial ischaemia to produce the severe exertional headache as its only main presenting symptom. This report presents a patient with myocardial ischaemia presenting solely with excruciating exertional occipital headache without associated chest discomfort. Previous reported cases and detailed pathophysiology are also reviewed.
Case report
A 58-year-old male dentist had a 2-month history of left occipital exertional headache. It began within a few minutes of starting his brisk walk or driving during a rush hour. The pain was severe, sharp shooting in character and originated in his left occipital area without radiation. This excruciating pain lasted 15–20 min in each attack and prevented him from maintaining the activity. There was no associated aura, photophobia, nausea or vomiting. Also, he never experienced chest discomfort or other cardiovascular symptoms during these exertional headaches.
He had previously been a healthy man without past and family history of headache and cardiovascular disease, except for two episodes of transient cerebral ischaemic attack 20 years ago. He had a long history of heavy smoking and a sedentary life style. Physical examination revealed normal blood pressure, heart rate and rhythm, systemic and neurological examinations. Benign exertional headache was the initial diagnosis. Amitriptyline, then additional flunarizine and analgesics failed to control the symptom. One month later the symptom developed during rest and rarely associated with mild chest tightness. He was seen by a local cardiologist and routine electrocardiogram revealed slight ST-T segment elevation along V1–3 with left axis deviation.
He was treated for ischaemic heart disease with isosorbide dinitrate 20 mg/day and aspirin 60 mg/day initially with partial response until 10 months later, when his headache was worse again. At this time he experienced occasional chest tightness and associated headache. The dosage of anti-anginal medications was titrated by the cardiologist without satisfactory response. He also developed the symptom during an excited night dream of chasing a robber.
Finally, he was referred to a cardiac centre in Bangkok and underwent further investigation and management. The first exercise stress test was positive at the low level and terminated by dyspnoea. Coronary angiogram revealed 50% occlusion of the distal left main trunk, and total occlusion of the proximal 1/3 of the left anterior descending artery, 70% occlusion of the proximal first obtuse marginal branch and total occlusion of the mid part of the right circumflex artery. Left ventricular ejection fraction of 74% and good collateral supply were identified. Coronary artery bypass graft surgery was performed at all sites of stenotic arteries 1 week later without complications. The symptom of exertional headache totally disappeared. He took aspirin 60 mg and propanolol 20 mg/day as secondary prophylaxis. Follow-up exercise stress tests at 6 months and 4.5 years post operation revealed negative results, also a thallium exercise test revealed no definite myocardial perfusion defect at 16 months after surgery.
Discussion
Sampson and Cheitlin (1) have proposed that the primary cardiac pain was mediated neurally by unknown pain-producing factors, which stimulated sensory nerve endings in coronary vessels. Bradykinin, a polypeptide usually produced by ischaemic tissue, could be a pain-producing factor in angina (3). Poor compliance of ischaemic myocardium causing lung congestion (4), ischaemic myocardial wall dyskinesia (5), coronary vasospasm (6), physiobiochemical changes at the interface area between normal and ischaemic tissue (7), and the inability of diseased coronary vessels to dilate sufficiently to meet the demand under sympathogenic stimulation (8) were the pathophysiological mechanisms proposed.
Once the cardiac pain originates, it is mediated through the sympathetic ganglions from C8 to T5 level in 50–60% of patients, through the vagal nerves in 10–20%, and through both systems in 30–40% (9). These afferent sympathetic and/or vagal neural pathways in convergence with somatic input from the areas of the body developed from the same embriogenic segments as the heart could explain the manifestation of cardiac pain and its referral areas on the body (10). In the rare presentation of unusual sites of referred pain, it was proposed as a variation in neural convergence from the somatic input, or an ‘overflow’ of the somatic convergence up or down the common neural segments involved (11). Also, the referred pain originating in the areas supplied by the trigeminal nerve could be explained by the ascent of convergence between the autonomic input and the somatic input from par caudalis, the descending sensory tracts of the trigeminal nucleus which reaches the C2–3 level, by vagal synaptic connection (12). Other proposed mechanisms include the rising of intracardiac pressure caused intracranial hypertension; and the potent cerebral vasodilators released by the ischaemic myocardium causing headache (13).
Typical angina pectoris occurred in 94% of cases with cardiac pain, while headache was found in only 6% during anginal attack, usually associated with chest discomfort (1). Some serious intracranial (but not extracranial) causes producing exertional headache have been identified, e.g. posterior fossa tumour, Arnold–Chiari malformation and syringomyelia ect (14). So, it is very unusual for myocardial ischaemia to produce only exertional headache as its first clinical manifestation.
Most of the reported cases of headache caused by myocardial ischaemia had associated chest discomfort during the attack (13, 15−19). There were only a few cases in which headache was the sole presenting complaint (11, 20). The patient reported here was also free from cardiac symptoms during presentation. Resting electrocardiogram in these cases usually revealed non-specific abnormalities (11, 13, 15, 17, 18). It was only by exercise stress test that the myocardial ischaemia was disclosed and frequently the headache was reproducible during the positive test (11, 13, 16, 19, 20). Cardiac angiogram commonly revealed three-vessel disease and the patient dramatically responded to coronary angioplasty or bypass surgery (11, 13, 16, 19). These findings were also found in this reported case, except for the reproducible headache during the positive exercise stress test (Table 1).
Summarizes the reported cases of exertional headache caused by myocardial ischaemia
The diagnosis of benign exertional headache should be made with special caution by excluding all possible serious causes. The emergence of resting headache and even vague chest tightness in this reported case should alert the attending physician to other differential diagnoses. It is crucial to recognize the unusual form of exertional headache which can be fatal and needs prompt management.