«ATTENTIONAL BIAS IN PATIENTS WITH IMPLANTABLE CARDIOVERTER DEFIBRILLATORS: EXAMINING MECHANISMS OF HYPERVIGILENCE AND ANXIETY By NEHA K. DIXIT A ...»
Sudden cardiac death is an increasingly frequent occurrence among patients with cardiovascular disease, particularly those with conditions compromising the electrophysiology of the heart. Recent advances in device technology have increased delivery of preferred treatment of life-threatening arrhythmias. A patient is considered at risk for sudden death if they have had a previous cardiac arrest from which they have been resuscitated, if they have an ejection fraction 35%, if they have a history of congestive heart failure, or have congenital cardiac issues such as long QT syndrome exist, where sudden death is a common outcome. ICDs are devices that prevent the heart from either going into a life threatening rhythm or shock the heart back from a chaotic rhythm. Sears and colleagues (1999, 2000, 2001, 2002, 2003, 2004), as well as other researchers, have discussed aspects of psychosocial distress related to living with an ICD. The two domains which have been commonly examined are affective and mood disturbances in patients and quality of life changes in patients. Sears (2003) has reported that the prevalence of anxiety symptoms in ICD patients is between 13-87% with rates of clinically-significant anxiety ranging between 15-38%. Rates of depression in this population are around 12-24%.
One of the interesting issues surrounding psychosocial distress in ICD patients is in the way one can attribute the distress. The CABG-PATCH trial, examined the quality of life and psychosocial distress in recipients of ICDs versus those who did not receive ICD post bypass surgery. Researchers in this study noted significant distress among the ICD group compared to the non-ICD group. Examining these data more thoroughly revealed that it was patients who received shocks who perceived their quality of life as diminished and contributed to the distress ratings in the group. Several other researchers have also implicated shock as an important contributor to psychosocial distress. Schron et al. (2004) showed that patients who got shocked in the first 6 months of receiving their device had a greater incidence of depression and anxiety than their non-shocked counterparts. Several other factors have been implicated in poor psychosocial functioning in recipients of ICDs including age, gender, premorbid psychological functioning, and general life coping skills (Sears et al, 1999). Pauli and colleagues (1999) have shown that individuals who adopt a coping style involving catastrophizing have more psychosocial distress and are less able to cope with both their device but also the aspects of having a life threatening condition. Such types of distress may manifest themselves in the inability to adequately manage treatment regimens, and intake of vital medical information. The accuracy of disease perception is critical to quality of life and survival of ICD patients.
Psychosocial Effects of ICD Implantation Patients with life threatening arrhythmias face numerous medical and psychosocial challenges in today’s environment. As stated previously, the advent of technology allows patients to live longer and more resilient medical lives, but in many patients the ICD comes at a price to their quality of life and mental health. Specifically, psychosocial and quality of life issues that coincide with implantation are being more carefully dissected.
Anxiety and the ICD Patient Anxiety has been identified as a significant contributor to the pathogenesis of cardiac disease (Kubzansky, Kawachi, Weiss, & Sparrow, 1998). Through activation of the sympathetic nervous system and subsequent release of catecholamines, anxiety is implicated in platelet aggregation, injury of arterial lining, and release of fatty acids into the blood – all of which promote the atherosclerotic process. Anxiety also may cause injury by decreasing heart rate variability and increasing the incidence of ventricular premature beats, thereby contributing to electrical instability. Finally, anxiety may trigger a myocardial infarction (heart attack) due to the association between hyperventilation and coronary vasospasms. Behavioral mechanisms have also been established associating anxiety with health-compromising activities, such as smoking, decreased physical activity, or poor diet (Haywood, 1995; Januzzi, Stern, Pasternak, & DeSanctis, 2000).
Anxiety is the most common complaint among ICD patients who have been shocked. A number of studies have shown that recipients of ICDs experience psychological distress as a result of receiving one or multiple shocks. The role of classical conditioning in the presence of a predominantly neutral stimulus (non-shock ICD placement) plays an important role in the development of anxiety and psychological symptoms (Sears et al, 1999; Godemann, 2004).
When an arrhythmia occurs, the patient receives a high-voltage shock to the chest. This is intuitively an anxiety-provoking and fearful experience for patients (Herrman, von zur Muhen, Schaumann, Buss, Kemper, Wantzen, & Gonska, 1997; Luderitz, Jung, Deister, & Manz, 1996;
Schuster, Phillips, Dillon, & Tomich, 1998; Sears, Todaro, Saia-Lewis, Sotile, & Conti, 1999).
Research indicates that excessive cardiac worry, ICD-specific fears, as well as physiological arousal are among the anxiety symptoms experienced by patients with ICDs (Sears et al., 2000).
Research has shown that up to 15.9% of patients who receive an ICD develop one or more anxiety disorders (e.g., panic disorder, generalized anxiety disorder) after implantation (Godemann et al, 2004). Accordingly, as many as 40% of ICD patients may exhibit clinically significant symptoms of anxiety (Sears & Conti, 2002).
Arrhythmias and Hypervigilance Living with arrhythmias of any kind can be as stressful as living with other chronic illness. What makes arrhythmias even more difficult to live with is the specific nature of the symptoms they produce. A patient with atrial arrhythmia, for example, may feel fluttering of the heart, tightness in the chest, and dizziness, among other symptoms. They may also feel nothing.
However, the consequence of their particular arrhythmia may be life threatening. Most patients with atrial fibrillation (a common arrhythmia in the elderly population) are on anti-coagulant therapy due to the high rates of thrombolic strokes which occur in these patients secondary to their arrhythmia. In the same regard, a patient with diagnosed susceptibility to supra ventricular tachycardia (SVT), ventricular tachycardia (VT), or ventricular fibrillation (VF) may feel dizzy, faint, have difficulty breathing and feel like their heart is racing. If these patients have ICDs, in most cases the response to their arrhythmia will be shock. Not surprisingly, it is not only the seriousness of the condition itself in patients with arrhythmias that contributes to anxiety and psychosocial distress, but the nature of the symptoms which are often themselves anxiety provoking (Burke, 2004). For example, Godemann (2004) found that ICD patients who had been shocked were three times more likely to have diagnosable panic disorder and generalized anxiety disorder than their non-shocked counterparts. Evidence from the ICD literature (Pauli, 1999, Sears and Conti, 2003) shows that patients are constantly evaluating their level of health.
Negative cognitions such as “will I die from this shock?” or “will by heart stop beating?” are acceptable and real questions for patients to ask themselves. The nature of their illness requires them to question their bodies. Problems arise when patients go from healthy questioning of symptoms to an unhealthy hypervigilence of their bodies. These individuals focus so much on factors determining their health status (e.g. checking their pulse, counting respirations, trying to predict shock), that they forgo living and general quality of life. Mallioux and Brenner (2002) described this phenomenon as “somatosensory amplification” in which patients overemphasize the responses of their parasympathetic nervous systems to normal stimuli and then worry about their health after making an inaccurate attribution. The illusion of control which is maintained by patients who are exceptionally anxious or hypervigilent is dangerous because it is not real. It is not based on actual physical merit and can actually cause increased numbers of arrhythmias, thus perpetuating the cycle of vigilance and distress.
Anxiety as Precipitant to Shock Recent research in the ICD literature points to growing evidence that stress and anxiety are themselves contributers to shock. A study by Shedd and colleagues (2004) examined the incidence of shocks 30 days before the attacks on world trade center and 30 days post. Findings demonstrated a 2.8 fold increase in shock after the WTC attacks among people living in Florida, while researchers examining individuals in New York City and other parts of New York found similar results at a 2.4 fold increase. Both studies controlled for other mitigating factors which may have contributed to shocks. These numbers indicate that traumatic life events even far from their occurrence increase stress and cause arrhythmias to occur. Dunbar (1999) also showed a relationship between aggression, hostility and shocks leading to the suggestion that there are patient relevant personality/trait factors which contribute to shock. Neurochemical support of these findings has been demonstrated by Lampert and colleagues (2004) who showed that higher levels of stress hormones (epinephrine and norephinephrine) were correlated with arrhythmic changes in the heart suggesting a biochemical pathway which may be excited when a patient gets anxious or stressed. Collectively, greater insights into anxiety processes may allow for some impact on the occurrence of shock itself.
Selective Attention Selective attention is an important component of a human’s cognitive experience. The brain’s ability to make decisions about what information to attend to and what information to filter out is vital to maneuvering through the vast array of environmental and internal stimuli we perceive and take in. Several researchers have examined different models of attention. Posner’s model of attention is well known to decompose the components of selective attention and aid in the understanding of mechanisms that comprise this system. This model of attention views attention as a system comprised of several voluntary and involuntary processes (Posner & Peterson, 1990; Posner & Raichle, 1994), which act in concert to orient a person to their environment. Selective attention is driven by the posterior attentional system that is defined as the “reactive” component of attention that orients a persons’ focus from one location to another.
According to Posner, orienting is accomplished through three operations: disengagement from the object, movement to another location, and engagement of that new location. This model theorizes that visual spatial attention involves both facilitation and inhibition of various competing visual information. In his seminal exogenous cueing task, Posner (1988) found that presentation of a visual cue increases a subject’s vigilance and orients them to that spatial location, thus allowing for faster target detection in that location. While a subject orients to the new location, he/she inhibits all other spatial information. Classical paradigms used to examine selective attention and orienting, have utilized Posner’s exogenous cueing paradigm and his theoretical principles in the experimental setting.
Attentional Bias and Emotion Affective influences on information processing is critical for human function. The adaptive function of emotion depends upon the particular emotion being studied but basic emotions such as anger, fear, happiness, sadness, and disgust evolved distinctly to benefit the human experience (LeDoux, 1996; Lang, Davis, & Ohman, 2000). For example, it is likely that the basic emotion of fear evolved to enable an organism to rapidly detect and respond to danger in its environment (LeDoux, 1996). Contemporary theories of emotion argue that the initial appraisal of a situation or object (as neutral, positive, or negative) is one of the major determinants of the emotional response to that situation (Lazarus, 1966; Oatley & Johnson-Laird, 1987). Since emotional appraisal of an external stimulus may also determine its importance or priority, attentional input to that stimulus may be guided by such an appraisal (Lang, Bradley, & Cuthbert 1997; Damasio, 1998; Compton, 2003). Thus, given the vast amount of information in our external environment it is adaptive for emotional processing of stimuli and attentional selection to be integrally related.
Of particular interest to researchers who examine the interplay between emotion and attention is the speed with which appraisals and attentional shifts are made. For example, several researchers have demonstrated that emotional processing is encoded early in the processing stream and is fairly “automatic” (Ohman, 1997, Zajonc, 2000). Automatic processing has been defined by a time frame between 100-300 milliseconds after the appearance of an emotional stimulus (Compton, 2003). Neuroimaging techniques have allowed researchers to examine brain activity during these early stages of processing. One such technique is event-related potentials (ERPs) which record fast electrical changes in the scalp during stimulus presentation. Studies using ERPs have demonstrated that discrimination of emotional content (e.g. face recognitionhappy, sad, angry; provocative pictures) occurs during as early as 80-160 milliseconds with the onset of the stimulus (Broomfield & Turpin (2005). Masking studies, where the emotional stimulus is imperceptible to conscious processing (Lang, Davis, & Ohman, 2000), have also demonstrated early detection of both the content of emotional stimuli (pleasant, neutral, or unpleasant) and intensity of the emotional connotation (arousal).