B P7 C71 Hypotension and Syncope Flashcards
Syncope is a symptom that presents with _____.
(1) Abrupt, transient, complete loss of consciousness (LOC)
(2) Associated with the inability to maintain postural tone
(3) With rapid and spontaneous recovery
The presumed mechanism of syncope is _____.
Cerebral hypoperfusion
It is important to recognize that syncope, as previously defined, represents a subset of a much wider spectrum of conditions that can result in transient LOC, including conditions such as cerebrovascular accident (stroke) and epileptic seizures.Nonsynco- pal causes of transient LOC differ in their mechanism and duration.
The metabolism of the brain, in contrast to that of many other organs, is exquisitely dependent on perfusion. Consequently, cessation of cerebral blood flow leads to LOC______. Restoration of appropriate behavior and orientation after a syncopal episode is usually immediate. Retrograde amnesia, although uncommon, can be present in older adults.
within approximately 10 seconds
The prognosis of patients with syncope varies greatly with the diag- nosis. Patients with syncope in the setting of structural heart disease or primary electrical disease have an increased incidence of SCD and overall mortality.Syncope caused by orthostatic hypotension is associated with two fold increase in mortality,which reflects the presence of multiple comorbid conditions in this patient group. In contrast, young patients with neurally mediated syncope (NMS) have an excellent prognosis.
_____, are by far the most common causes and account for at least one third of all syncopal episodes.
Vascular causes of syncope, particularly reflex-mediated syncope and orthostatic hypotension
Standing upright displaces _____ of blood to the abdomen and lower extremities, thereby resulting in an abrupt drop in venous return. to the heart. This drop leads to a decrease in cardiac output and stim- ulation of aortic, carotid, and cardiopulmonary baroreceptors, which triggers a reflex increase in sympathetic outflow. As a result, _____, ______, _______ to maintain stable systemic blood pressure (BP) on standing.
500 to 800 mL
Heart rate, cardiac contractility, and vascular resistance increase
This is a term used to refer to the signs and symptoms of an abnormality in any portion of this BP control system
Orthostatic intolerance
Orthostatic hypotension is defined as a ______ of standing.
Orthostatic hypotension can be asymptomatic or associated with syncope, lightheadedness/ presyncope, tremulousness, weakness, fatigue, palpitations, diaphoresis, and blurred or tunnel vision.
Many patients with orthostatic hypotension are asymptomatic despite substantial falls in systolic BP and low upright BPs.
These symptoms are often worse immediately on arising in the morning or after meals or exercise.
20-mm Hg drop in systolic BP or a 10-mm Hg drop in diastolic BP within 3 minutes
Initial orthostatic hypotension is defined as less _____ immediately on standing with rapid (<30 seconds) return to normal. In contrast, delayed progressive orthostatic hypotension is characterized by a slow progressive decrease in systolic BP on standing.
Less than a 40-mm Hg decrease in BP
Syncope that occurs after meals,particularly in older adults,can result from a redistribution of blood to the gut. A _____ has been reported in up to one third of older adult nursing home residents. Although usually asymptomatic, it can result in lightheadedness or syncope.
Decline in systolic BP of approximately 20 mm Hg approximately 1 hour after eating
Drugs that either cause ____ or ______ are the most common causes of orthostatic hypotension (Table 71.3).
Older adult patients are particularly susceptible to the hypotensive effects of drugs because of reduced baroreceptor sensitivity,decreased cerebral blood flow, renal sodium wasting, and an impaired thirst mechanism that develops with aging
Volume depletion or result in vasodilation
There are three types of primary autonomic failure.
______ is an idiopathic sporadic disorder characterized by orthostatic hypotension, usually in conjunction with evidence of more widespread autonomic failure, such as disturbances in bowel, bladder, thermoregulatory, and sexual function. Patients with pure autonomic failure have reduced supine plasma norepinephrine levels.
______ is a sporadic, progressive, adult-onset disorder characterized by autonomic dysfunction,parkinsonism,and ataxia in any combination.
The third type of primary autonomic failure is ____. A small subset of patients with Parkinson disease may also experience autonomic failure, including orthostatic hypotension.
Pure autonomic failure (Bradbury-Eggleston syndrome)
Multisystem atrophy (Shy-Drager syndrome)
Parkinson disease with autonomic failure
In addition to these forms of chronic autonomic failure is a rare, ______. This neuropathy generally occurs in young people and results in severe, widespread sympathetic and parasympa- thetic failure with orthostatic hypotension, loss of sweating, disruption of bladder and bowel function,fixed heart rate,and fixed dilated pupils.
Acute panautonomic neuropathy
____ is a clinical syndrome characterized by frequent symptoms that occur with standing (e.g., lightheadedness, palpitations, tremulousness, generalized weakness, blurred vision, exercise intolerance, fatigue), an increase in heart rate of _____ (or 40 beats/min in those 12 to 19 years of age), and _______
Postural orthostatic tachycardia syndrome (POTS)
Increase in HR of 30 beats/min or more on standing
Absence of a more than 20-mm Hg reduction in systolic BP
In this group of conditions, the cardiovascular reflexes that control the circulation become inappropriate in response to a trigger, which results in vasodilation with or without bradycardia and a drop in BP and global cerebral hypoperfusion. In each case the reflex is composed of a trigger (the afferent limb) and a response (the efferent limb).
Reflex-mediated syncope/Situational syncope
If hypotension secondary to peripheral vasodilation predominates, it is classified as a _____ response; if bradycardia or asystole predominates, it is classified as a _____; and when both vasodilation and bradycardia play a role, it is classi- fied as a mixed response
Vasodepressor response - peripheral vasodilation
Cardioinhibitory response - bradycardia or asystole
Mixed - mixed response
The two most common types of reflex-mediated syncope are _____.
Carotid sinus hypersensitivity
Neurally mediated hypotension
The term neurally mediated hypotension or syncope (also known as neurocardiogenic, vasodepressor, and vasovagal syncope and “faint- ing”) has been used to describe a common abnormality in regulation of BP characterized by an abrupt onset of hypotension with or without bradycardia
Triggers associated with the development of NMS include orthostatic stress, such as can occur with prolonged standing or a hot shower, and emotional stress, such as can result from the sight of blood.1
It has been speculated that the fall in BP seen during neurally mediated hypotension mimics a “fictitious hemorrhage.” To protect against this fictitious hemorrhage, the brainstem triggers cardioinhibition as pro- tection against the hypothetical loss of blood simulated by the reduc- tion in venous return.
Syncope caused by ____ results from stimu- lation of carotid sinus baroreceptors located in the internal carotid artery above the bifurcation of the common carotid artery.
It is diag- nosed by the reproduction of clinical syncope during carotid sinus massage, with a cardioinhibitory response if asystole is longer than 3 seconds or AV block occurs; or a significant vasodepressor response if there is a more than 50-mm Hg drop in systolic BP; or a mixed cardioinhibitory and vasodepressor response
Carotid sinus hypersensitivity
Thus the diagnosis of carotid sinus hypersensitivity should be approached cautiously after excluding alternative causes of the syncope. Once diagnosed, dual-chamber pacemaker implantation is recommended for patients with recurrent syncope or falls resulting from carotid sinus hypersensitivity that is cardioinhibitory or mixed (class 2A/IIa,level of evidence [LOE] B-R)
Cardiac causes of syncope, particularly tachyarrhythmias and bradyarrhythmias, are the second most common cause of syncope and account for 10% to 20% of syncopal episodes (see Table 71.2 and Chapters 65 and 67).
_____ is the most common tachyarrhythmia that can cause syncope.
VT
Neurologic causes of transient LOC, including migraines, seizures, Arnold-Chiari malformations, and transient ischemic attacks, are surprisingly uncommon and account for less than 10% of all cases of syncope.
Most patients in whom a “neurologic” cause of transient LOC is established are in fact found to have had a ______ rather than true syncope.
Seizure
Metabolic causes of transient LOC are rare and account for less than 5% of syncopal episodes.
The most common metabolic causes of syncope are _______. Establishing hypoglycemia as the cause of apparent LOC requires demonstration of hypoglycemia during the syncopal episode. Although hyperventilation-induced syncope has generally been considered to result from a reduction in cerebral blood flow, one study demonstrated that hyperventilation alone was not sufficient to cause syncope.
Hypoglycemia, hypoxia, and hyperventilation
The 2017 ACC/AHA/HRS syncope guidelines provide a class I (LOE B-NR) recommendation for performing a detailed history and physical examination in patients with syncope.
Initial evaluation should begin by determining whether the patient did in fact experience a syncopal epi- sode by asking the following: (1) Did the patient experience complete LOC? (2) Was the LOC transient with a rapid onset and short duration? (3) Did the patient recover spontaneously, completely, and without sequelae? and (4) Did the patient lose postural tone?
f the answer to one or more of these questions is negative, other nonsyncopal causes of transient LOC should be suspected.
When evaluating a patient with syncope,particular attention should then be focused on (1) determining whether the patient has a _____ (i.e., diabetes) or a family history of cardiac disease, syncope, or sudden death; (2) identifying medications that may have played a role in syncope, especially those that may cause hypo- tension, bradycardia/heart block, or a proarrhythmic response (anti- arrhythmics); (3) quantifying the number and chronicity of previous syncopal and presyncopal episodes; (4) identifying precipitating fac- tors,including body position and activity immediately before syncope; and (5) quantifying the type and duration of prodromal and recovery symptoms.
History of cardiac disease or metabolic disease
Family history - CD, Syncope, SCD
Medications
Number/chronicity
Precipitating factors
Type and duration