B P7 C68 Bradyarrhythmias and AV Blocks

Question 1

Based on large population studies of healthy individuals, the lower limit of normal resting heart rate is defined as ___ beats/min.

Answer 1

50 bpm

Question 2

Frequently, bradyarrhythmias are physiologic, as in _____. In other cases, bradyarrhythmias can be pathologic

Answer 2

Well-conditioned athletes with low resting heart rates

Type I atrioventricular (AV) block during sleep

Question 3

Sinus bradycardia is diagnosed in an adult when the sinus node discharges at a rate less than ___ beats/min. P waves have a normal contour, and are usually upright in leads I, II, and aVF, and occur before each QRS complex, usually with a constant PR interval longer than 120 msec. Sinus arrhythmia often coexists.

Answer 3

< 50 bpm

Question 4

Sinus bradycardia can result from _____. In most cases, symptomatic sinus bradycardia is caused or worsened by the effects of medication.

Answer 4

Excessive vagal or decreased sympathetic tone
Effect of medications
Anatomic changes in the sinus node

Question 5

During sleep, the normal heart rate can fall to _____ beats/min, especially in adolescents and young adults, with marked sinus arrhythmia sometimes producing pauses of ___ seconds or longer

Answer 5

35 to 40 bpm

Sinus arrhythmia 2s or longer

Question 6

Causes of sinus bradycardia

Answer 6

Eye surgery
Coronary arteriography
Meningitis
Intracranial tumors
Increased intracranial pressure
Cervical and mediastinal tumors
Certain disease states (e.g., severe hypoxia, myxedema, hypothermia, fibrodegenerative changes, convalescence from some infections, gram-negative sepsis, mental depression
Vomiting
Vasovagal syncope
Carotid sinus stimulation
Administration of parasympathomimetic drugs, lithium, amiodarone, beta adrenoceptor–blocking drugs, clonidine, propafenone, ivabradine, or calcium antagonists

Question 7

In most cases, sinus bradycardia is a benign arrhythmia that can actually be beneficial by producing a _____, especially in heart failure patients. Conversely, it can be associated with syncope caused by an abnormal autonomic reflex

Answer 7

Longer period of diastole and increasing ventricular filling time

Question 8

Sinus bradycardia occurs in _____% of patients with acute myocardial infarction (MI) and may be even more prevalent when patients are seen in the early hours of infarction. Unless it is accompanied by hemodynamic decompensation or arrhythmias, sinus bradycardia is generally associated with _____ outcome after MI than sinus tachycardia.

Answer 8

10% to 15%

More favorable

Question 9

SB is usually transient and occurs more commonly during _____than during anterior MI; sinus bradycardia has also been noted during reperfusion with thrombolytic agents.

Bradycardia that follows resuscitation from cardiac arrest is associated with a _____.

Answer 9

Inferior

Poor prognosis: SB after arrest

Question 10

Sinus arrhythmia is characterized by a phasic variation in sinus cycle length during which the maximum sinus cycle length minus the minimum sinus cycle length exceeds ____ msec or the maximum sinus cycle length minus the minimum sinus cycle length divided by the minimum sinus cycle length exceeds ____%

Answer 10

> 120 ms (CLmax-CLmin)

> 10% (CLmax-CLmin/CLmin)

Question 10

Treatment of sinus bradycardia is not usually necessary unless cardiac output is inadequate or arrhythmias result from the slow rate.

_____ (0.5 mg intravenously as an initial dose, repeated if necessary) is generally acutely effective; lower doses, particularly given SC or IM, can exert an initial parasympathomimetic effect, possibly by a central action.

For recurrent symptomatic episodes, _____ may be needed.

Although _____ can be used to increase the sinus rate, as a general rule, no drugs are available that increase the heart rate reliably and safely during long periods without undesirable side effects.

Answer 10

Atropine

Recurrent: temporary or permanent pacing

Theophylline and terbutaline

Question 11

It is the most frequent form of arrhythmia and is physiologically normal. P wave morphology does not usually vary, and the PR interval exceeds 120 msec and remains unchanged because the focus of discharge remains relatively fixed within the sinus node. On occasion, the pacemaker focus can wander within the sinus node, or its exit to the atrium may change and produce P waves of a slightly different contour (although not retrograde) and a slightly changing PR interval that exceeds 120 msec.

Answer 11

Sinus arrhythmia

Question 12

Nonrespiratory sinus arrhythmia is characterized by a phasic variation in the P-P interval unrelated to the respiratory cycle and can be the result of _____

Answer 12

Digitalis intoxication

Question 12

In the respiratory form, the P-P interval cyclically shortens during _____, primarily as a result of reflex inhibition of vagal tone, and slows during _____; breath-holding eliminates the variation in cycle length

Answer 12

Inspiration: Shorter P-P
Expiration: Slowing

Question 13

Loss of sinus rhythm variability is a risk factor for _____

Answer 13

SCD

Question 14

Marked sinus arrhythmia can produce a sinus pause sufficiently long to cause syncope if it is not accompanied by an escape rhythm. Treatment is usually unnecessary.

Increasing the heart rate by _____ generally abolishes sinus arrhythmia. Symptomatic individuals may experience relief from palpitations with _____, as for the treatment of sinus bradycardia.

Answer 14

Exercise or drugs

Sedatives, tranquilizers, atropine, ephedrine, or isoproterenol administration

Question 15

The P-P interval delimiting the pause ____ a multiple of the basic P-P interval.

Answer 15

Does not equal

Question 15

The most common example of ventriculophasic sinus arrhythmia occurs during _____, when P-P cycles that contain a QRS complex are shorter than P-P cycles without a QRS complex. Similar lengthening can be present in the P-P cycle that follows a premature ventricular complex (PVC) with a compensatory pause. Alterations in the P-P interval are probably caused by the influence of the autonomic nervous system responding to changes in ____.

Answer 15

Complete AV block and a slow ventricular rate

Ventricular stroke volume

Question 16

Failure of sinus nodal discharge results in the _____ and can also result in _____ if escape beats initiated by latent pacemakers do not occur. Involvement of the sinus node by acute MI, degenerative fibrotic changes, digitalis toxicity, stroke, or excessive vagal tone can produce sinus arrest.

Answer 16

Absence of atrial depolarization

Ventricular asystole

Question 17

As a general rule, chronic pacing for sinus bradycardia is indicated only in _____ patients.

Answer 17

Symptomatic

Question 18

_____ is an arrhythmia that is recognized electrocardiographically by a pause resulting from absence of the normally expected P wave. The duration of the pause is a multiple of the basic P-P interval.

This block is caused by a conduction disturbance during which an impulse formed within the sinus node fails to depolarize the atria or does so with delay

Answer 18

SA exit block

Question 19

An interval without P waves that equals approximately two, three, or four times the normal P-P cycle characterizes _____-degree SA exit block.

Answer 19

Type II second-degree SA exit block

Question 20

During _____ second-degree SA exit block, the P-P interval progressively shortens before the pause, and the duration of the pause is less than two P-P cycles

Answer 20

Type I (Wenckebach) second-degree SA exit block

Question 21

_____ SA exit block cannot be recognized on the electrocardiogram (ECG) because SA nodal discharge is not recorded.

Answer 21

First-degree

Question 22

_____ SA exit block can be manifested as a complete absence of P waves and is difficult to diagnose with certainty without sinus node electrograms.

Answer 22

Third-degree

Question 23

_____, can produce SA exit block. SA exit block is usually transient. It may be of no clinical importance except to prompt a search for the underlying cause. On occasion, syncope can result if the SA block is prolonged and unaccompanied by an escape rhythm. SA exit block can occur in well-trained athletes.

Answer 23

Excessive vagal stimulation
Acute myocarditis
MI
Fibrosis involving the atrium
Drugs such as quinidine, procainamide, flecainide, and digitalis

Question 24

Sick sinus syndrome is a term applied to a syndrome encompassing several sinus nodal abnormalities, including:

Answer 24

(1) Persistent spontaneous sinus bradycardia inappropriate for the physiologic circumstance
(2) Sinus arrest or exit block
(3) Combinations of SA and AV conduction disturbances
(4) Alternation of paroxysms of rapid regular or irregular atrial tachyarrhythmias and periods of slow atrial and ventricular rates (bradycardia-tachycardia syndrome)

Question 25

The anatomic basis of sick sinus syndrome can involve _____.

Fibrosis and fatty infiltration occur, and the sclerodegenerative processes generally involve the sinus node and the AV node or the bundle of His and its branches or distal subdivisions. Occlusion of the sinus node artery can cause sinus node dysfunction.

Answer 25

(1) Total or subtotal destruction of the sinus node
(2) Areas of nodal-atrial discontinuity
(3) Iflammatory or degenerative changes in the nerves and ganglia surrounding the node
(4) Pathologic changes in the atrial wall

Question 26

_____ is diagnosed when the heart rate does not increase appropriately in the setting of increased physiologic demand

Answer 26

Chronotropic incompetence (CI)

Question 27

Although many studies for chronotropic incompetence use a definition of failure to obtain _____% of either maximal expected heart rate, or of inadequate heart rate reserve (the difference between resting heart rate and age predicted maximal heart rate), the variance in individual heart rate range can require meticulous clinical assessment

Answer 27

80% or 85%

Question 27

_____ is the principal determinant of rate of oxygen consumption (VO2) and exercise capacity.The fourfold increase in VO2 during exercise is largely due to a 2.2-fold increase in heart rate. Genome-wide association studies have confirmed heritability of heart rate increase with exercise and heart rate recovery.

Answer 27

Increase in heart rate due to physiologic demand

Question 28

_____ alone can confer CI; the age-related decline in heart rate response to exercise is inevitable even in healthy older athletes.

Answer 28

Aging

Question 29

_____ occurs when a patient has tachyarrhythmias and bradyarrhythmias closely associated in time. That can occur when a tachyarrhythmia, typically atrial fibrillation or atrial flutter terminates, with a resultant excessive post-conversion pause.

Answer 29

Tachycardia-bradycardia syndrome (TBS)

Question 30

For patients with sick sinus syndrome, treatment depends on the basic rhythm problem but usually involves permanent pacemaker implantation when symptoms are manifest. ____ for bradycardia, combined with drug therapy to treat the tachycardia, is required in those with bradycardia-tachycardia syndrome.

Answer 30

Pacing for bradycardia + Drug therapy for tachycardia for TBS

Question 31

TBS can also occur during atrial fibrillation when periods of atrial fibrillation with rapid ventricular rates alternate with periods of excessive bradycardia (due to high-grade AV block) during atrial fibrillation.

While TBS can occur without medication, it typically occurs as a result of treatment with _____.

Answer 31

Beta blockers or calcium channel blockers.

Question 32

_____ is a disturbance of impulse conduction that can be permanent or transient, depending on the anatomic or functional impairment. It must be distinguished from interference, a normal phenomenon that is a disturbance of impulse conduction caused by physiologic refractoriness resulting from inexcitability secondary to a preceding impulse.

Answer 32

Heart Block

Question 33

AV block is classified by severity into three categories. _____.The degree of block may depend in part on the direction of impulse propagation.For unknown reasons, retrograde conduction can still occur in the presence of advanced anterograde AV block.

Answer 33

During first degree heart block, conduction time is prolonged but all impulses are conducted.

Second-degree heart block occurs in two forms, Mobitz type I (Wenckebach) and type II.Type I heart block is characterized by gressive lengthening of the conduction time until an impulse is not conducted.Type II heart block denotes an occasional or repetitive sudden block of conduction of an impulse, without prior measurable lengthening of conduction time.

When no impulses are conducted, complete or third-degree block is present

Question 34

Some electrocardiographers use the term _____ to indicate blockage of two or more consecutive impulses.

Answer 34

Advanced or high-grade heart block

Question 35

During first-degree AV block, every atrial impulse is conducted to the ventricles and a regular ventricular rate is produced, but the PR interval exceeds _____ second in adults.

PR intervals as long as 1.0 second have been noted and can at times exceed the P-P interval, a phenomenon known as _____

Answer 35

0.20

Skipped P waves

Question 36

Acceleration of the atrial rate or enhancement of vagal tone by carotid massage can cause first-degree AV nodal block to progress to _____ AV block. Conversely, type I second-degree AV nodal block can revert to a _____ block with deceleration of the sinus rate.

Answer 36

Type I second-degree AVB

first-degree

Question 37

Blocking of some atrial impulses conducted to the ventricle at a time when physiologic interference is not involved defines _____.

Answer 37

Second- degree AV block

Question 38

Electrocardiographically, typical type I second- degree AV block is characterized by _____, whereas in type II second-degree AV block, the ______.

Answer 38

Type I 2nd degree AVB: progressive PR prolongation culminating in a nonconducted P wave

Type II 2nd degree AVB: PR interval remains constant before the blocked P wave

Question 39

During a typical type I block, the increment in conduction time is greatest in the second beat of the Wenckebach group, and the absolute increase in conduction time decreases progressively over sub- sequent beats. These two features serve to establish the characteristics of classic Wenckebach group beats: ______.
Although much emphasis has been placed on this characteristic grouping of cycles, primarily to be able to diagnose a Wenckebach exit block, this typical grouping occurs in fewer than 50% of patients with a type I Wenckebach AV nodal block.

Answer 39

(1) the interval between successive beats progressively decreases, although the conduction time increases (but by a decreasing function)

(2) the duration of the pause produced by the nonconducted impulse is less than twice the interval preceding the blocked impulse (which is usually the shortest interval)

(3) the cycle that follows the nonconducted beat (beginning the Wenckebach group) is longer than the cycle preceding the blocked impulse.

Question 40

Type II AV block often antedates the development of _____, whereas type I AV block with a normal QRS complex is generally more benign and does not progress to more advanced forms of AV conduction disturbance.

Answer 40

Adams-Stokes syncope and complete AV block

Question 41

In a patient with an acute MI, type I AV block usually accompanies _____ infarction (perhaps more often if a right ventricular infarction also occurs),is transient, and does not require temporary pacing, whereas type II AV block occurs in the setting of acute ____ MI, can require temporary or permanent pacing, and is associated with high mortality, generally as a result of pump failure

Answer 41

Type I AVB: inferior infarction (transient, does not require pacing)

Type II AVB: anterior MI (Can require pacing, associated with high mortality)

Question 42

A _____ of AV block can occur in patients with acute inferior MI and is associated with more myocardial damage and a higher mortality rate than in those without AV block.

Answer 42

High degree

Question 43

First-degree and type I second-degree AV block can occur in _____, as noted earlier, probably related to an increase in resting vagal tone

Answer 43

Normal healthy children

Wenckebach AV block can be a normal phenomenon in well-trained athletes

Question 43

In patients who have chronic second-degree AV nodal block (proximal to the His bundle) without structural heart disease, the course is generally benign (except in older age groups),whereas in those with _____ the prognosis is poor and related to the type and severity of the underlying heart disease.

Answer 43

Structural heart disease,

Question 44

High-grade, or “advanced,” AV block is differentiated from complete AV block by an _____, yet conduction that is more impaired than in second-degree AV block

Answer 44

Intermittent relationship between atrial and ventricular activity

Question 45

The ventricular rhythm will not be regular since the diagnosis of high-grade AV block requires demonstration of _____. Commonly, ____ consecutive non-conducted P waves are noted on ECG

Answer 45

Intermittent AV conduction

2 or more

Question 46

Etiologies of high grade AV block include _____. The clinical presentation, symptoms, and outcomes are indistinguishable from third-degree AV block.

Answer 46

Acute coronary syndromes
Rheumatic heart disease
Autoimmune disorders
Myocarditis
Infiltrative cardiomyopathies

Question 47

Third-degree or complete AV block occurs when _____ and therefore the atria and ventricles are controlled by independent pacemakers. Thus, complete AV block is one type of complete AV dissociation.

Answer 47

No atrial activity is conducted to the ventricles

Question 48

Sites of ventricular pacemaker activity that are in or closer to the His bundle appear to be more _____ rate than those located more distally in the ventricular conduction system.

Answer 48

Stable and can produce a faster escape

Question 49

The ventricular rate in acquired complete heart block is less than _____ beats/min but can be faster with congenital complete AV block

Answer 49

Acquired CHB: <40 bpm

Congenital: Faster

Question 50

Complete AV block can result from a block at the level of the AV node, within the bundle of His, or distal to the His in the Purkinje system. Block proximal to the His bundle generally exhibits normal QRS complexes and rates of _____ beats/min because the escape focus that controls the ventricle arises in or near the His bundle.

Answer 50

40 to 60 bpm

Question 51

In patients with AV nodal block, _____ generally speeds both the atrial and the ventricular rate.

Exercise can reduce the extent of AV nodal block.

Answer 51

Atropine

Question 52

Acquired complete AV block occurs most often _____ to the bundle of His because of trifascicular conduction disturbance. Each P wave is followed by a His deflection, and the ventricular escape complexes are not preceded by a His deflection. The QRS complex is abnormal, and the ventricular rate is generally less than _____ beats/min.

Answer 52

Distal

<40 bpm

Question 53

Paroxysmal AV block in some cases can be caused by exaggerated responsiveness of the AV node to _____.

Surgery, electrolyte disturbances, myoendocarditis, tumors, Chagas disease, rheumatoid nodules, calcific aortic stenosis, myxedema, polymyositis, infiltrative processes (e.g., amyloidosis, sarcoidosis, scleroderma), and an almost endless assortment of common and unusual conditions can produce complete AV block

Answer 53

Vagotonic reflexes

Question 54

In adults, rapid rates may be followed by block (called _____ AV block), which is thought to result from phase _____ block (block caused by incomplete action potential recovery), postrepolarization refractoriness, and concealed conduction in the AV node

Answer 54

Tachycardia-dependent AVB

Phase 3

Question 55

Less common than tachycardia-dependent AV block, _____ AV block can also occur; it results in AV block after a pause or during relative bradycardia and thus can be difficult to distinguish from vagal AV block. This form of AV block is often referred to as a phase _____ block because it is thought that spontaneous depolarizations during the resting phase of the action potential result in an inability to depolarize, although other mechanisms may also play a role.

Answer 55

Pause-dependent paroxysmal AVB

Phase 4

Question 56

In children, the most common cause of AV block is _____. In such circumstances, the AV block can be an iso- lated finding or associated with other lesions. Neonatal autoimmune disease, from maternal antibodies crossing the placenta, accounts for most cases of heart block in utero or in the immediate neonatal period but only for rare cases of congenital heart block occurring after this period

Answer 56

Congenital

Question 57

Many of the signs of AV block are evident at the bedside.

First-degree AV block can be recognized by a _____ a to c wave interval in the jugular venous pulse and by diminished intensity of the _____ as the PR interval lengthens

Answer 57

Long a to c wave interval

Diminished intensitiy of the first heart sound (S1)

Question 58

In type I second- degree AV block, the heart rate may increase imperceptibly with gradually diminishing intensity of S1; widening of the a to c interval, terminated by a pause; and an a wave not followed by a v wave.

Answer 58

(1) heart rate may increase imperceptibly with gradually diminishing intensity of S1;
(2) widening of the a to c interval, terminated by a pause;
(3) a wave not followed by a v wave

Question 59

_____ characterize type II AV block. S1 maintains a constant intensity.

In complete AV block, the findings are the same as those in AV dissociation.

Answer 59

Intermittent ventricular pauses and a waves in the neck not followed by v waves

Question 60

Significant clinical manifestations of first- and second-degree AV block usually consist of palpitations or subjective feelings of the heart _____.

Answer 60

“missing a beat.”

Question 61

Complete AV block can be accompanied by signs and symptoms of _____

Answer 61

Reduced cardiac output
Syncope or presyncope
Angina
Palpitations from ventricular tachyarrhythmias

Question 62

For patients with transient or paroxysmal AV block and presyncope or syncope, the diagnosis can be elusive.

_____ can be useful, but monitoring for longer periods may be necessary, with extended (>3 weeks) Holter or external loop recorders being required.

Longer periods of recording require an _____ to establish the diagnosis.

In patients with presyncope or syncope, one should suspect intermittent infrahisian block in those with BBB or an intraventricular conduction defect. An _____ to evaluate AV conduction thoroughly (including infusion of isoproterenol and/or procainamide) may be warranted to make the diagnosis, particularly in those with severe symptoms

Answer 62

Ambulatory monitoring (Holter or external loop recorders)

Implantable loop recorder

EPS

Question 63

Drugs cannot be relied on to increase the heart rate for more than several hours to several days in patients with symptomatic heart block without producing significant side effects. Therefore, _____ is indicated for patients with symptomatic bradyarrhythmias.

Answer 63

Temporary or permanent pacemaker insertion

Question 64

For short-term therapy, when the block is likely to be evanescent but still requires treatment or until adequate pacing therapy can be established, vagolytic agents such as _____ are useful for patients who have AV nodal disturbances, whereas _____ such as isoproterenol can be used transiently to treat patients who have heart block at any site.

Isoproterenol should be used with extreme caution or not at all in patients with acute MI.

Answer 64

Atropine

Catecholamines

Question 65

For symptomatic AV block or high-grade AV block (e.g., infrahisian, type II AV block, third-degree heart block not caused by congenital AV block), _____ is the treatment of choice.

There is growing evidence that some patients with AV block, especially those with preexisting left ventricle dysfunction, may benefit from _____ pacing rather than right ventricle– only pacing to prevent the development or progression of symptoms caused by heart failure

Answer 65

Permanent pacemaker placement

Biventricular

Question 66

As the term indicates, _____ defines AV dissociation. AV dissociation is never a primary disturbance of rhythm but rather is a “symptom” of an underlying rhythm disturbance produced by one of three causes or a combination of causes that prevents the normal transmission of impulses from atrium to ventricle

Answer 66

Dissociated or independent beating of the atria and ventricles

Question 67

The ECG in AV dissociation demonstrates the _____. P wave morphology depends on the rhythm controlling the atria—sinus, atrial tachycardia, junctional, flutter, or fibrillation.

During complete AV dissociation, both the QRS complex and the P waves appear to be regularly spaced without a fixed temporal relationship to each other.

Answer 67

Independence of P waves and QRS complexes

Question 68

Physical findings in AV dissociation include _____

_____ waves may be seen in the jugular venous pulse when atrial and ventricular contractions occur simultaneously.

The second heart sound can split normally or paradoxically, depending on the manner of ventricular activation.

A premature beat representing ventricular capture can interrupt a regular heart rhythm. When the ventricular rate exceeds the atrial rate, a cyclic increase in intensity of the first heart sound is produced as the PR interval shortens, climaxed by a very loud sound (bruit de canon).

This intense sound is followed by a sudden reduction in intensity of the first heart sound and the appearance of giant a waves as the PR interval shortens and P waves “march through” the cardiac cycle.

Answer 68

(1) Variable intensity of the first heart sound as the PR interval changes
(2) Atrial sounds
(3) a waves in the jugular venous pulse lacking a consistent relationship to ventricular contraction

Intermittent large (cannon) a waves

Question 69

Since the sinus node and AV node are richly innervated by the autonomic nervous system, both sinus bradyarrhythmias (sinus pauses,sinus arrest, and sinus arrhythmia) and AV block (typically type I AV block, or intermittent complete block) can be caused by _____ influences without any underlying conduction system disease.

Answer 69

Autonomic

Question 70

Increases in parasympathetic (vagal) tone can be triggered by a variety of events that can result in bradyarrhythmias and include _____ and others

Answer 70

Hypersensitive carotid sinus syndrome
Vasovagal syncope
Cough syncope
Stimulation of the Bezold-Jarisch receptors during an inferior MI
Autonomic dysfunction

Question 71

Neurally-mediated bradyarrhythmias are characterized most frequently by _____caused by cessation of atrial activity as a result of sinus arrest or SA exit block

Answer 71

Ventricular asystole

Question 72

In symptomatic patients, AV junctional or ventricular escapes generally do not occur or are present at very slow rates, suggesting that heightened vagal tone and sympathetic withdrawal can _____ subsidiary pacemakers located in the ventricles, as well as in supraventricular structures.

Answer 72

Suppress

Question 73

There are generally two types of neutrally mediated responses, and frequently both occur in the same patient to varying degrees.

A _____ response is generally defined as ventricular asystole exceeding 3 seconds, although normal limits have not been definitively established. In fact, asystole exceeding 3 seconds during carotid sinus massage is not common but can occur in asymptomatic subjects.

A _____ response is usually defined as a decrease in systolic blood pressure (SBP) of 50 mm Hg or more without associated cardiac slowing or a decrease in SBP exceeding 30 mm Hg when the patient’s symptoms are reproduced.

Answer 73

Cardioinhibitory

Vasodepressor

Question 74

_____ acutely abolishes cardioinhibitory responses to neurally mediated bradyarrhythmias. However, symptomatic patients with a cardioinhibitory response may benefit from pacemaker implantation. Because AV block can occur with a cardioinhibitory response, some form of _____ is generally required.

Answer 74

Atropine

Ventricular pacing, with or without atrial pacing,

Question 75

Atropine and pacing do not prevent the SBP decrease in the vasodepressor response, which may result from _____.

Answer 75

Inhibition of sympathetic vasoconstrictor nerves and possibly from activation of cholinergic sympathetic vasodilator fibers.

Question 76

Patients who have neurally mediated bradyarrhythmias that do not cause symptoms require ___ treatment.

Drugs such as _____ can enhance neurally mediated bradyarrhythmias and be responsible for symptoms in some patients.

Answer 76

No

dDigitalis, methyldopa, clonidine, and propranolol

Question 77

_____ may be helpful in patients with vasodepressor responses.

Answer 77

Elastic support hose and sodium-retaining drugs