Download Cardiac Pacing in First-Degree Atrioventricular Block

Cardiac Pacing in First-Degree
Atrioventricular Block
Serge Barold, Bengt Herweg
Florida Heart Rhythm Institute, Tampa, Florida, USA.
ABSTRACT
This article will summarize the cardiac pacing in first-degree atrioventricular block.
K EYWORDS
Cardiac pacing, first-degree atrioventricular block
Birinci Derece Atriyoventriküler Blokta Kalp Pili
ÖZET
Bu yazıda birinci derece atriyoventriküler blokta kardiyak pacing özetlenecektir.
A NAHTAR K ELİMELER
Birinci derece atriyoventriküler blok, kardiyak pacing
İLETİŞİM ADRESİ
Dr. Serge BAROLD
Florida Heart Rhythm Institute, Tampa, Florida, USA
Cardiac Pacing in First-Degree Atrioventricular Block
F
irst-degree atrioventricular (AV) block, often considered a relatively benign arrhythmia, can occasionally be associated with severe symptoms. Although there is little evidence to suggest that pacemakers improve survival
in patients with isolated first-degree AV block,
it is now recognized that marked (PR ≥ 0. 30 sec)
first-degree AV block can lead to symptoms similar to those in the pacemaker syndrome even
in the absence of higher degrees of AV block
(1-4). Uncontrolled trials have shown that many
symptomatic patients with a PR interval ≥ 0.30
sec can be improved with dual chamber pacing
especially in patients with normal left ventricular (LV) function.
45
Echocardiography
Prolonged AV conduction causes atrial
systole too early in diastole which then causes
an ineffective or decreased contribution of atrial systole to cardiac output. Such a decrease
in cardiac output is poorly tolerated in heart
failure patients. Atrial contraction begins in
early diastole resulting in atrial systole superimposed upon the early left ventricular (LV)
filling phase and much earlier than the onset
of LV systolic pressure. There is therefore delay of the E wave with resultant fusion between the E and A waves producing shortening of
the LV diastolic filling time (Fig 1). The delay
in AV conduction also induces diastolic mit-
FİGURE 1
Pulsed wave Doppler echocardiography coupled with the surface ECG in a patient with a long PR interval. Left panel: The E and
A waves are superimposed due to the very late diastole resulting from a very delayed ventricular activation. Right panel: Dual
chamber pacing results in shortening of the AV interval (from atrial sensing to onset of ventricular pacing). The E wave now occurs
well before the A wave (atrial contraction). This increases the left ventricular filling time and the aortic velocity-time integral (VTI).
(Reproduced with permission from Garrigue S. Optimization of cardiac resynchronization therapy: the role of echocardiography
in atrioventricular, interventricular and intraventricular delay optimization. In: Yu CM, Hayes DL, Auricchio A (Eds), Cardiac
Resynchronization Therapy, Malden, MA, Blackwell-Futura, 2006:310-328).
CİLT 9, SAYI 1, Şubat 2011
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Türk Aritmi, Pacemaker ve Elektrofizyoloji Dergisi
ral regurgitation (Fig 2). In a normal heart, atrial systole occurs immediately before ventricular systole. In the setting of a long PR interval, the atrium begins to relax and atrial pressure drops after atrial systole. This causes the
mitral valve to remain open because of delayed LV systole. With the mitral valve open,
the LV end-diastolic pressure rises and exceeds left atrial pressure thereby producing diastolic mitral regurgitation, a decrease in preload
(LV end-diastolic pressure) at the onset of LV
systole and, ultimately, a decrease in LV dP/dt
max and cardiac output. This type of mitral regurgitation appears inconsequential in the normal heart but may be important in patients with
severe LV dysfunction.
Pacemaker-like Syndrome
AAI(R) pacing with a very long PR interval
may produce pacemaker syndrome. This form
of pacemaker syndrome has resurfaced more
recently in patients with intermittent marked
first-degree AV block during managed ventricular pacing to minimize right ventricular pacing. In this pacing mode, a device permits the
establishment of very long PR intervals without
the emission of a ventricular output.
A long PR interval (≥ 0.30 sec) without a
pacemaker shares the same pathophysiology
as VVI pacing with retrograde ventriculoatrial conduction or an AAI-induced pacemaker
syndrome. Some workers have called the hemodynamic disturbance produced by marked
FİGURE 2
Continuous-wave Doppler echocardiographic recording of transmitral blood flow velocity demonstrating diastolic mitral
regurgitation in a patient with first degree AV block with a markedly prolonged PR interval of 360 msec. The low velocity
regurgitant signal is seen in diastole following the atrial filling wave and prior to the onset of systolic mitral regurgitation. CİLT 9, SAYI 1, Şubat 2011
Cardiac Pacing in First-Degree Atrioventricular Block
first-degree AV block a “pacemaker syndrome
without a pacemaker”, and others have labeled
this entity as “pseudopacemaker syndrome.”
These characterizations are potentially confusing. The term “pacemaker-like” syndrome is
probably more appropriate.
Although patients with symptomatic marked
first-degree AV block (≥ 0.30 sec), and normal
LV function can benefit from dual chamber pacing. Some patients with a long PR interval and
interatrial conduction delay may be already hemodynamically compensated because delayed
conduction to the left atrium may be associated
with an appropriately timed mechanical left AV
synchrony, a situation where improvement would not be expected with pacing.
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sis. An acute determination of the clinical status and need for permanent pacing can often
be made noninvasively Occasionally a therapeutic decision may be facilitated by an invasive hemodynamic study with temporary right
atrial and ventricular pacing to assess the hemodynamic response to AV interval optimization (Fig 3). However, an acute hemodynamic
Clinical evaluation.
Patients with marked first-degree AV block
may or may not be symptomatic at rest. They
are more likely to become symptomatic with
mild or moderate exercise when the PR interval
does not shorten appropriately and atrial systole shifts progressively closer towards the preceding LV systole. Patients with subtle symptoms
should undergo a treadmill stress test to determine the hemodynamic disadvantage of the
long PR interval (defined as ≥ 0.30 sec). In some
patients the long PR interval itself may occasionally become manifest only on exercise. Adaptation of the PR interval on exercise is unlikely
in patients with a PR interval ≥ 0.30 sec.
In symptomatic patients with marked 1stdegree AV block (as an isolated abnormality) it
is important to realize that the benefit of pacing
with optimized AV synchrony (with a shorter
AV delay) may outweigh the risk of impaired
LV function produced by right ventricular pacing with resultant LV dyssynchrony. This risk
is impossible to evaluate on a short-term ba-
FİGURE 3
Hemodynamic abnormalities in a symptomatic patient with
marked first-degree AV block and hemodynamic improvement
with temporary dual chamber pacing. A. Pulmonary capillary
wedge pressure shows large cannon waves during sinus rhythm
with a very long PR interval (Scale 0-40 mmHg). B. Note the
normal pulmonary capillary wedge pressure after temporary
dual chamber pacing with a physiologic AV delay (Scale 0-40
mm Hg). (Reproduced with permission from Barold SS. Acquired
atrioventricular block. In: Kusomoto FM, Goldschlager N (Eds),
Cardiac Pacing for the Clinician, Philadelphia, PA, Lippincott
Williams and Williams, 2001;229-251).
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Türk Aritmi, Pacemaker ve Elektrofizyoloji Dergisi
FİGURE 4
Twelve-lead ECG in the same patient as in Fig 3. During sinus tachycardia the sinus P wave is close to the preceding QRS
complex on the initial portion of the ST-segment. This pattern mimics a reentrant supraventricular tachycardia. . (Reproduced
with permission from Barold SS. Acquired atrioventricular block. In: Kusomoto FM, Goldschlager N (Eds), Cardiac Pacing for the
Clinician, Philadelphia, PA, Lippincott Williams and Williams, 2001;229-251).
improvement with a more physiologic AV delay does not guarantee long-term benefit because of the potential risk of harmful long-term effects of continual right ventricular pacing. Furthermore, it may be impossible during a resting
pacing study to demonstrate symptomatic improvement, and the performance of an exercise study with a temporary dual-chamber pacemaker in place is difficult. Therefore it is reasonable to recommend a permanent pacemaker
in many symptomatic patients without a temporary pacing study which itself carries unnecessary risks and cost.
misinterpreted to show a junctional rhythm
with retrograde ventriculoatrial conduction
(Fig 4). In questionable cases, sinus rhythm
can be easily documented during an electrophysiologic study by delineating the pattern of right atrial activation which travels from high to low right atrium in sinus
rhythm (Fig 5).
2. Patients with a long PR interval may respond
to the abnormal resting hemodynamics with
sinus tachycardia which may be misinterpreted as supraventricular tachycardia because the P-wave is placed so close to the preceding QRS complex.
Asymptomatic patients
There are no data on the prognosis of asymptomatic patients with a long PR interval
(≥ 0.30 sec). Pacing is generally not recommended in truly asymptomatic patients.
Differential diagnosis
1. The diagnosis of marked first-degree AV
block can be overlooked when the PR interval is very long because the ECG may be
CİLT 9, SAYI 1, Şubat 2011
AV delay vs. asynchronous ventricular
activation
Optimization of the AV interval may be
harmful in some patients because of deterioration of LV function secondary to paced ventricular depolarization. It is unwise to program a
slow pacing rate and a very long AV delay to
avoid right ventricular pacing in a patient who
remains symptomatic. Programming a short AV
Cardiac Pacing in First-Degree Atrioventricular Block
49
FİGURE 5
Figure 5. Surface ECG and intracardiac recording from a patient with symptomatic marked first-degree AV block. Same patient as
in Figures 3 and 4. RA = high right atrial electrogram, HBE = electrogram at site of His bundle recording. Note the sequence of
atrial activation (RA to HBE) is consistent with sinus rhythm and rules out retrograde atrial activation. The AH interval is markedly
prolonged. (Reproduced with permission from Barold SS. Acquired atrioventricular block. In: Kusomoto FM, Goldschlager N (Eds),
Cardiac Pacing for the Clinician, Philadelphia, PA, Lippincott Williams and Williams, 2001;229-251).
delay for hemodynamic benefit requires periodic evaluation of LV function to determine the
cumulative effect of right ventricular pacing.
Long PR interval, and congestive heart
failure
Studies with conventional DDD pacing and
a short AV delay in heterogeneous groups of patients with LV systolic function and congestive heart failure of various etiologies have generally yielded disappointing results. In only
a few patients with severe congestive heart failure and first-degree AV block, implantation of a conventional dual chamber pacemaker
may occasionally improve cardiac performance
but DDD pacing may also cause further longterm deterioration of LV function secondary
to pacing-induced abnormal LV depolarization. . Conventional DDD pacing abolishes presystolic mitral regurgitation and increases the time
for forward flow. However, elimination of diastolic mitral regurgitation plays as yet an undefined but probably small role in the overall he-
modynamic benefit but it may result in more
optimal hemodynamic performance because of
a lower left atrial pressure and higher LV preload at the onset of systole. Long-term deterioration of LV function during DDD or DDDR pacing may eventually necessitate an upgrade to
biventricular pacing.
Indications for Pacing
The 2008 ACC/AHA/HRS Guidelines (3)
state: “Although there is little evidence to suggest that pacemakers improve survival in patients with isolated first-degree AV block, it is
now recognized that marked (PR more than 300
milliseconds) first-degree AV block can lead to
symptoms even in the absence of higher degrees of AV block. When marked first-degree AV
block for any reason causes atrial systole in close proximity to the preceding ventricular systole and produces hemodynamic consequences
usually associated with retrograde (ventriculoatrial) conduction, signs and symptoms similar
to the pacemaker syndrome may occur. With
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Türk Aritmi, Pacemaker ve Elektrofizyoloji Dergisi
marked first-degree AV block, atrial contraction occurs before complete atrial filling, ventricular filling is compromised, and an increase in
pulmonary capillary wedge pressure and a decrease in cardiac output follow. Small uncontrolled trials have suggested some symptomatic and
functional improvement by pacing of patients
with PR intervals more than 0.30 seconds by
decreasing the time for AV conduction. Finally,
a long PR interval may identify a subgroup of
patients with LV dysfunction, some of whom
may benefit from dual-chamber pacing with a
short(er) AV delay. Although echocardiographic or invasive techniques may be used to assess hemodynamic improvement before permanent pacemaker implantation, such studies are
not required. The table in the guidelines shows
that first-degree AV block is a class IIa indication as follows: Permanent pacemaker implantation is reasonable for first- or second-degree AV
block with symptoms similar to those of pacemaker syndrome or hemodynamic compromise.” It would seem more prudent at this juncture
to consider the initial implantation of a biventricular DDD device when the LV ejection fraction is ≤ 35% even in the presence of a narrow
QRS complex.
The guidelines of the European Society of
Cardiology (4) state that: “In patients with firstdegree AV block, cardiac pacing is not recommended unless the PR interval fails to adapt to
heart rate during exercise and is long enough
(usually .300 ms) to cause symptoms becauseof
inadequate LV filling, or an increase in wedge
pressure, as the left atrial systole occurs close to
or simultaneous with the previous LV systole.
In such cases small, uncontrolled studies have
shown an improvement in patients’symptoms.”
The guidelines also recommend pacing with a
IIa indication.
R EFERENCES
1. Barold SS. Indications for permanent cardiac pacing
in first-degree AV block: class I, II, or III? Pacing Clin
Electrophysiol 1996;19:747-51.
2. Barold SS, Ilercil A, Leonelli F, Herweg B. Firstdegree atrioventricular block. Clinical manifestations,
indications for pacing, pacemaker management & consequences during cardiac resynchronization. J Interv Card
Electrophysiol 2006;17:139-52.
3. Epstein AE, DiMarco JP, Ellenbogen KA, et al.
Guideline Update for Implantation of Cardiac Pacemakers
and Antiarrhythmia Devices); American Association for
Thoracic Surgery; Society of Thoracic Surgeons. ACC/
AHA/HRS 2008 Guidelines for Device-Based Therapy of
Cardiac Rhythm Abnormalities: a report of the American
College of Cardiology/American Heart Association Task
Force on Practice Guidelines (Writing Committee to
CİLT 9, SAYI 1, Şubat 2011
Revise the ACC/AHA/NASPE 2002 Guideline Update for
Implantation of Cardiac Pacemakers and Antiarrhythmia
Devices) developed in collaboration with the American
Association for Thoracic Surgery and Society of Thoracic
Surgeons. J Am Coll Cardiol 2008;51:e1-62.
4. Vardas PE, Auricchio A, Blanc JJ, et al. European
Society of Cardiology; European Heart Rhythm
Association. Guidelines for cardiac pacing and cardiac
resynchronization therapy. The Task Force for Cardiac
Pacing and Cardiac Resynchronization Therapy of the
European Society of Cardiology. Developed in collaboration with the European Heart Rhythm Association.
Europace 2007;9:95