Cardiac Manifestations of Selected Neurologic Disorders
Kenneth W. Mahaffey
Daniel Laskowitz
Introduction
Cardiac manifestations of neurologic disorders are common and diverse. Understanding the pathophysiology of cardiac and neurologic disorders is critical for physicians caring for patients with cardiovascular and neurologic disease states and investigators attempting to develop therapies and management strategies for disorders that have both central nervous system and cardiovascular components. The importance of interactions between cardiology and neurology are exemplified by ongoing collaborative efforts between cardiologists and neurologists in several key clinical areas, including stroke prevention in atrial fibrillation, percutaneous intervention in cerebrovascular occlusive disease, and the use of thrombolytic and antiplatelet therapies in nonhemorrhagic stroke. Many of these specific issues are discussed in other chapters. In this chapter, the focus is on cardiac manifestations of specific central nervous system events and the cardiac anomalies associated with hereditary and acquired neuromuscular disorders.
Cardiac Manifestations of Neurologic Events
It was over 70 years ago that Beattie et al. (1) recognized that the central nervous system had neurogenic input in cardiac arrhythmias. Soon after, Aschenbrenner and Bodechtel (2) reported electrocardiographic (ECG) abnormalities in young patients with brain lesions and presumed normal cardiac structure. It is now commonly known that ECG abnormalities can occur in the setting of central nervous system abnormalities such as ischemic stroke, intracranial hemorrhage, seizure, headache, meningitis, encephalitis, and cranial trauma. Generally, these ECG features can be interpreted correctly in the setting of known or suspected neurologic disease. However, the erroneous diagnosis of primary cardiac disease can occur and more importantly result in inappropriate therapy or delay in proper treatment. Substantial work has been done to attempt to understand the pathophysiology of these cardiac manifestations.
Acute Ischemic Stroke
Cardiovascular complications are extremely common following stroke and represent a major form of morbidity. These complications may be caused by focal cerebral injury or may be a manifestation of preexisting cardiac disease, which is common.
Several studies have documented a high prevalence of ECG changes and arrhythmias in patients with acute ischemic stroke. Common ECG changes include QT prolongation, T-wave abnormalities, prominent U waves, and ST-segment abnormalities (Table 35D.1) (3,4,5,6,7). The prevalence of asymptomatic coronary artery disease in patients with symptomatic cerebrovascular disease has been reported to be as high as 28% to 65% (8,9). Thus, cerebrovascular disease may be a marker for coronary artery disease that becomes clinically apparent during the physiologic stress of acute ischemic stroke. Few studies have systematically examined old tracings to establish if the ECG changes were new (10).
Arrhythmias are also common after acute ischemic stroke (see Table 35D.1). Atrial fibrillation has been most frequently described, although it is often unclear whether the atrial fibrillation was the cause of a cardioembolic event or secondary to cerebral infarction (3,10,11). Ventricular ectopy has also been frequently reported, although episodes of sustained ventricular tachycardia are distinctly uncommon. Atrioventricular (AV) block has been reported and has been attributed to excessive vagal stimulation (12). Intensive monitoring of patients presenting with acute stroke has increased the recognition of these arrhythmias, but has not been shown to reduce morbidity or mortality. Because life-threatening arrhythmias in these patients are uncommon, it may be difficult to show a clear benefit. Prolonged cardiac monitoring, however, may be a useful diagnostic tool and routine ECG evaluation may identify the approximately 15% of patients with acute ischemic stroke who may suffer a myocardial infarction (13,14).
TABLE 35D.1 Reported electrocardiographic changes and arrhythmias in patients with intracranial hemorrhage or ischemic stroke | ||
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Intracranial Hemorrhage
Byer in 1947 (15) first reported large T waves and QT prolongation in a patient with subarachnoid hemorrhage. The first systematic review of ECGs in patients with intracerebral or subarachnoid hemorrhage was done in 1954 and reported that QT prolongation, increased T-wave amplitude, and abnormal U waves were the most common abnormalities (16). Others have reported similar changes (see Table 35D.1) (17,18).
The precise incidence of specific ECG abnormalities is not known because reports have included patients with diverse baseline clinical characteristics and lesion types but rates vary from 50% to 98% (3,10,17,19). Although there is no definitive correlation between hemorrhage location and specific ECG changes, several studies have noted an association between frontal lobe hemorrhage and QT prolongation (5,20).
The largest comparative series evaluating ECG abnormalities in stroke patients included 150 stroke patients and 150 age- and gender-matched controls: 92% of stroke patients and 65% of controls had abnormal ECGs. Abnormal ECGs were found in 43 (98%) patients with intracranial hemorrhage. Few ECG findings characterized a particular stroke type. Atrial fibrillation was significantly more common in patients with cerebral embolus (47% versus 9% for other stroke type), and QT prolongation was most common in patients with subarachnoid hemorrhage (71% versus 39% for other stroke types). U waves were more common in patients with intracranial hemorrhage than in patients with other stroke types (25% versus 8%).
Supraventricular and ventricular arrhythmias as well as conduction abnormalities have been well documented in patients with intracranial hemorrhage (see Table 35D.1). Several observational series have reported arrhythmias in 47% to 90% of patients (10,11,21,22) and serious or life-threatening arrhythmias in 20% to 50% of patients with intracranial hemorrhage (21,23,24,25).
A comprehensive evaluation of arrhythmias in stroke patients was reported by Di Pasquale et al. (21). Twenty-four–hour Holter monitor recordings were performed on 120 patients with subarachnoid hemorrhage: 96 of 107 patients (90%) with adequate recordings had arrhythmias (Table 35D.2). In general, arrhythmias are more frequent and severe in patients with recordings in the first 48 hours after onset of bleeding. The QTc interval more often prolonged with malignant ventricular arrhythmias. Hypokalemia is common and potassium levels were significantly lower in patients with ventricular arrhythmias. The presence of malignant ventricular arrhythmias or asystole has been reported as a univariable predictor of mortality after intracranial hemorrhage (10,26,27,28,29,30,31).
Management of Arrhythmias in Patients With Intracranial Hemorrhage or Ischemic Stroke
Management of patients with arrhythmias in the setting of intracranial hemorrhage has not been studied rigorously. Because of the high incidence of arrhythmias, continuous ECG monitoring is recommended, but there is no consensus about its required duration. Patients with QT prolongation should be monitored closely and possible causative factors such as medications or electrolyte abnormalities should be identified and corrected. Patients with Torsade de Pointes have been treated with atrial or ventricular overdrive pacing or isoproterenol. Left stellate ganglion block has also been proposed in patients with recurrent arrhythmias (32).
Intracranial Hemorrhage and Electrocardiographic Changes Consistent With Acute Myocardial Infarction
Multiple cases of patients with intracranial hemorrhage and ECG changes consistent with acute myocardial infarction and normal coronary anatomy by cardiac catheterization or at autopsy have been reported (33,34,35,36,37,38). Although a rare clinical entity, physicians need to be aware that ECG changes and symptoms consistent with myocardial ischemia or acute infarction may coexist with intracranial hemorrhage and a thorough history and physical examination are essential to avoid the catastrophic consequences of administering thrombolytic or anticoagulant therapy.
Mechanisms of Electrocardiographic Changes and Arrhythmias in Patients With Intracranial Hemorrhage or Ischemic Stroke
Substantial work in experimental models and humans has been done to try to understand the pathogenesis of the ECG changes seen in patients with cerebrovascular events. The first comprehensive report of central nervous system control of cardiovascular function was proposed over a century ago by Jackson (39). The most widely accepted mechanism by which lesions in the central nervous system result in changes in the ECG is a direct result of alterations in the autonomic nervous system control on cardiac electrophysiology. Several other processes are considered contributory, including a direct effect on the myocardium, consequences of the associated hemodynamic derangements, electrolyte abnormalities, alterations in circulating catecholamine levels, or concurrent coronary artery disease.
Experimental animal studies have strongly supported the belief that ECG changes associated with neurologic lesions are due, at least in part, to altered sympathetic tone. Stimulation of various brain structures has resulted in specific ECG changes similar to those seen in patients with ischemic stroke and intracranial hemorrhage (40,41,42,43,44,45,46,47,48,49,50,51).
TABLE 35D.2 Cardiac arrhythmias and transient ST-segment changes in 107 patients with subarachnoid hemorrhage and technically adequate Holter recording | |||||||||||||||||||||||||||||||||||||||||||||||
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