Page 216 - Cardiac Nursing

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192 PA R T I I / Physiologic and Pathologic Responses
decreased slow-wave sleep, reduced REM latency, an increased age. Although heart rate usually is lowest in slow-wave sleep, little
number of eye movements during REM periods, and increased information is available about sleep stage relationships with brad-
REM intensity. 265,268–270 yarrhythmias. REM sleep-related bradyarrhythmia syndrome is a
Major depression and SRBD, particularly CSR–CSA, are well- rare problem characterized by asystoles lasting several seconds
established risks for poor clinical outcomes and death in patients during REM sleep accompanied by alterations in sympathetic and
with CVD. Multiple mechanisms linking depression, sleep dis- parasympathetic bursts in otherwise healthy individuals. 274
turbances, and heart disease have been proposed. Depression low- Bradycardia-dependent changes in atrial repolarization predispos-
ers adherence to prescribed medications and increases unhealthy ing to intra-atrial re-entry have been suggested to lead to vagally
lifestyle behaviors among cardiac patients. Similar underlying mediated atrial fibrillation during sleep in susceptible patients. 275
hypothalamic–pituitary–adrenal axis, neuroendocrine, and im- Obesity increases the risk for OSA, specifically the magnitude of
mune dysregulation have been reported in both depression and nocturnal O 2 desaturation, and both are independent risk factors
sleep disturbances, further leading to a heightened risk for for incident atrial fibrillation in patients under the age of 65
arrhythmias and sudden death. 265,267,268 years. 276 Disruptions in sleep, increased night-time activity and
restlessness, daytime sleepiness and fatigue are present in atrial fib-
rillation patients and contribute to a reduced quality of life. 277,278
CARDIAC EVENTS IN SLEEP PVCs are common after MI and, when frequent or complex,
carry a higher mortality risk. Sleep usually suppresses arrhythmo-
Angina genesis and the frequency of PVCs in healthy people. Night-time
PVCs have no consistent relation to sleep stage in that some indi-
Anginal chest pain results from myocardial ischemia, an imbal- viduals experience greater numbers during the wake sleep transi-
ance between coronary blood flow and myocardial requirements. tion and others during REM. The frequency of PVCs; however,
In its classic form, angina is precipitated by physical exertion or may be independently related to heart rate and is increased by fac-
other situations that increase myocardial O 2 demand. Blood pres- tors such as hypoxemia, increased circulating catecholamines, and
sure and heart rate characteristically increase before appearance of loss of vagal activity during the night. Hypoxemia is especially im-
ischemic changes in the ECG in daytime and sleep-related angi- portant in patients with sleep apnea and COPD, in whom PVCs
nal episodes (see Chapter 15). are clearly more common during sleep than wakefulness.
Classic (effort) angina and the full spectrum of cardiac is- Patients with implantable cardioverter defibrillators and atrial
chemic syndromes including unstable angina, non-Q-wave MI, defibrillators may experience sleep disruption initially after im-
and variant angina occur more often in the morning hours and plant due to incisional pain and increased awareness of the device.
early after awakening than at night. 271 Sleep is generally a time of Sleep disruptions may be due to device activations, appropriate
reduced myocardial demand because of decreased blood pressure and inappropriate shocks. Atrial defibrillation therapy has not
and heart rate. However, in persons with stable coronary artery been found to affect sleep; however, atrial fibrillation symptoms
disease and normal left ventricular function, REM-induced surges and depression may contribute to sleep disruptions.
in heart rate can increase metabolic demands in the context of The impact of sleep disordered breathing in cardiac patients on
stenotic blood flow, thereby setting up a cascade of events that can arrhythmogenesis cannot be overemphasized. In the Sleep Heart
59
lead to plaque disruption and arrhythmias. Patients with known Health Study, individuals with severe sleep disordered breathing
daytime ischemia report relatively few night-time anginal episodes had two- to four-fold higher odds of complex arrhythmias in-
and usually have reduced or unchanged ECG evidence of is- cluding atrial fibrillation, ventricular tachycardia, and ventricular
chemia. Of all angina attacks, 50% occur within the initial ectopy than those without cardiac disease, even after adjusting for
6 hours after awakening with 74% associated with possible exter- potential confounding factors. 279 OSA as a cause of atrial fibrilla-
nal triggers such as physical activity or anger demonstrating a tion is not proven; however, in PSG studies of adults, both obe-
marked wake time-related circadian variation in the occurrence of sity and nocturnal O 2 desaturations independently predicted
angina pectoris attacks. 272 atrial fibrillation in subjects under the age of 65 years. 276 Appro-
Variant (Prinzmetal) angina is a less common form of ischemic priate treatment with CPAP in OSA patients is associated with
chest pain. It is caused by coronary artery spasm and is character- lower recurrence of AF. 280
ized by angina at rest and ST segment elevation. Variant angina
has a clear circadian rhythm, with episodes clustering in the early
morning hours of sleep. At one time, increased sympathetic activ- NURSING CARE GOALS
ity during REM sleep was believed to be the mechanism for noc-
turnal coronary spasm; however, more contemporary understand- After evaluating the subjective and objective data related to sleep
ings have emerged from research documenting circadian noted earlier in the chapter, a nursing assessment may indicate
alterations in endothelial function and reduced nocturnal vagal that a patient is experiencing sleep difficulties. A nursing diagno-
nerve and cardiac parasympathetic activity. 273 sis of impaired sleep is made when patients experience or are at
risk of experiencing a change in the quantity or quality of sleep
Arrhythmias that causes discomfort or interferes with daily life. The general
nursing management plan focuses on promoting adequate, restful
Sinus bradycardia and sinus arrhythmia are the most frequent sleep for patients with cardiovascular disorders. This can be ac-
changes in heart rhythm during sleep in healthy people, consistent complished first by preventing or reducing the factors that are dis-
with the dominance of parasympathetic activity. Bradycardia dur- turbing the patient’s sleep. A second goal is to provide bedtime
ing sleep is more common in men than in women, and the dif- routines, comfort measures, and a setting conducive to sleep. A
ference between daytime and night-time heart rates decreases with third goal is to detect alterations in physiological function that are