The Rate Dependent Bundle Branch Block

THE RATE DEPENDENT BUNDLE
BRANCH BLOCK
- Transition from Left Bundle Branch Block to Intraoperative
Normal Sinus Rhythm - Case Report -
Seema Mishra*, Prashant Nasa# , Gaurav Nirwani Goyal##,
Himanshu Khurana# , Deepak Gupta#
AND Sushma Bhatnagar **
**
**
***
****
Abstract
A chronic hypertensive patient with electrocardiogram (ECG) showing left bundle branch
block (LBBB) was given general anesthesia for right modified radical mastectomy. Her ECG
reverted to normal sinus rhythm intermittently during peri-operative period. This intermittent ratedependent LBBB is a rare entity. Though hypertension is one significant co-morbid condition, the
risk evalution of LBBB during anesthesia only on an ECG finding, is not justifiable. Rather patient
should be investigated further for any cardiac risk.
Keywords: Left bundle branch block, heart-intra ventricular conduction.
Introduction
Left bundle branch block is a major electrocardiographic abnormality in hypertensive patient.
It may signify associated coronary heart disease. Few cases have been reported on such ratedependent LBBB developing intraoperatively in a patient with normal ECG1-5 but without LBBB
preoperatively.
We report a case of preoperative LBBB which reverted to normal sinus rhythm below critical
hear rate, during perioperative period.
Case Report
A 45 year-old 70 kg female diagnosed as a case of carcinoma right breast T2N1Mx (Stage
2) was posted for modified radical mastectomy. Pre-anesthetic evaluation revealed that she was
a known case of hypertension of 6 yrs and was on oral losartan hydrochlorthiazide once a day,
with good control of blood pressure. She gave no history of chest pain, syncope or dyspnea on
exertion. On systemic examination, there was no significant abnormality in the cardiovascular and
respiratory systems.
From Unit of Anesthesiology, Institute Rotary Cancer Hospital (IRCH), Ansari Nagar, New Delhi, All India Institute of Medical
Sciences, Ansari Nagar, New Delhi India, Pin code: -110029.
*
MD, Assistant Professor Anaesthesia.
#
MD, Senior Resident Anaesthesia.
## Senior Research Associate Anaesthesia.
** Associate Professor Anaesthesia.
Corresponding author: Dr. Seema Mishra, Assist. Prof. Anesthesiology, F-33, AIIMS Residential Campus (West), Ansari
Nagar, New Delhi, Pin: 110029, India. Phone: +91-9899061105, Fax.91-11-26588641, E-mail: [email protected]
295
M.E.J. ANESTH 20 (2), 2009
296
Her investigations including complete hemogram,
renal function tests, blood urea, serum creatinine, blood
sugar, liver function test, serum bilirubin, and total
proteins, were within normal limits. Her ECG showed
LBBB. Fine needle aspiration cytology of right breast
was positive for ductal carcinoma. Ultrasonography
abdomen showed incidental finding of chronic
cholecystitis changes and cholelithiasis. Her bone scan
and chest ski gram were normal.
A Dobutamine-stress thallium/99mTc myocardial
perfusion imaging was done by a cardiologist whose
report revealed mildly hypoperfused anteroseptal region
(may be due to breast attenuation or LBBB) and there was
no evidence of stress induced ischemia. Left ventricular
ejection fraction was 66% (normal >65%) with mildly
hypokinetic anteroseptal region. She was taken up for
surgery and a mild risk explained to patient.
Premedication consisted of intramuscular
glycopyrrolate 0.2 mg, fentanyl 100 µg, and
promethazine 25 mg. The induction of general
anesthesia was done with intravenous propofol 2 mg/
kg-1 and fentanyl 2 µg/kg-1. Tracheal intubation 7.5
mm internal diameter cuffed endotracheal tube was
accomplished with intravenous vecuronium 0.1 mg/
kg-1. Anesthesia was maintained with oxygen, nitrous
oxide in 40:60 ratios and 0.5-1% isoflurane. The
patient was mechanically ventilated (tidal volume 8
ml/kg-1 and rate 12 breaths minute-1).
Intraoperatively after 25 minutes of anesthesia,
her ECG reverted to normal sinus rhythm with a
heart rate of 55 ± 3 beats per min, and blood pressure
maintained within normal limits. This reversal to normal
sinus rhythm was observed untill the time of reversal.
However, at the time of reversal of neuromuscular
blockade with inj. neostigmine 0.5 mg/kg-1 and inj.
glycopyrrolate 8 µg/kg-1, ECG started showing a repeat
pre-operative LBBB again with heart rate around 100
± 10 min-1. Total anesthesia time was 90 minutes.
In the ICU, the patient was monitored for one
hour postoperatively, her ECG again returned to
normal sinus rhythm for 10 min at a heart rate of 55 ±
5 min-1. However, soon ECG started showing LBBB
with no symptoms despite adequate pain relief and
normal to stable vital parameters at a heart rate 72
min-1 (Fig. 1).
Seema Mishra ET. AL
Fig. 1
Perioperative electrocardiograms showing intermittent ratedependent left bundle branch block
a) Pre perative
b) Intraoperative
c) During Reversal
d) Post Operative
THE RATE DEPENDENT BUNDLE BRANCH BLOCK
The postoperative period remained uneventful
except for asymptomatic LBBB. Holter examination
showed that the ECG changes were rate-dependent left
bundle branch block.
Discussion
Left bundle branch block is major clinical
finding in cases of known hypertension. It may also
signify associated coronary artery disease, aortic valve
disease or cardiomyopathies6. Isolated left bundle
branch block in a healthy young adult may be benign,
but in hypertensive or older patients it may signify
a progressive degenerating myocardium involving
cardiac conduction system7-9.
The stress-perfusion imaging of the patient
showed a relatively normal cardiac performance.
Her ECG which was showing LBBB preoperatively,
became normal peri-operatively at a heart rate of <60
beats per minute.
Our hypothesis is that the LBBB in the present
case was not of organic origin as proved by stressperfusion imaging and the fact that LBBB reverted
back to normal sinus rhythm. When heart rate was at 60
± 10 beats per minute intraoperatively, and especially
postoperatively for some time, LBBB reverted to sinus
rhythm. So pre-operative abnormal ECG rhythm was
rate-dependent LBBB, reverting into normal sinus
rhythm at lower heart rates (critical heart rates).
The rate-dependent bundle branch block is
defined as an intraventricular conduction defect that
may return, if only temporarily, to sinus rhythm at
lower heart rates9. The exact mechanism of such a
block is unclear but may result from anatomic or
physiological interruptions in cardiac conduction
system either due to ventricular enlargement or from
297
neurogenic or functional depression with or without
underlying pathological lesions of the conducting
tissue10. Rate-dependent bundle branch block can
revert to sinus rhythm at critical heart rate11. The
transition from normal to abnormal may occur by
alterations in heart rate by only 1 or 2 beats/min-10. This
critical heart rate is dependent on change in heart rate3.
With rapid decrease in heart rate, sinus rhythm may
appear at higher rates and with rapid acceleration in
heart rate, it may appear at lower heart rate, as the heart
rate increase RR interval shortens and the descending
impulses finds one of the bundle branches still in its
refractory period9.
A clear differentiation of LBBB into a benign
rate-dependent LBBB, and LBBB associated with
myocardial ischemia or infarction, may avoid the
unnecessary postponement of a case because of high
cardiac risk. Various convenient methods exist for the
diagnoses of rate-dependent LBBB during anesthesia.
Manouvers like carotid massage, deep inspiration and
pharmacological agents like esmolol12, metoprolol6,
propanolol, neostigmine and edrophonium which all
decrease the heart rate and thus change this aberrant
conduction block to normal13. Holter examination,
however, is the gold standard.
In a chronic hypertensive patient with LBBB,
it is always better to do further cardiac evaluation,
like stress-imaging, in order to rule out an associated
CAD.
In conclusion, rate-dependent left bundle branch
block is a rare entity. LBBB with other co morbid
condition, like hypertension, though a significant
finding, yet the evaluation of risk during anesthesia
only on an ECG finding, is not justifiable. Rather
patient should be further investigated for any associated
cardiac co morbid conditions.
M.E.J. ANESTH 20 (2), 2009
298
Seema Mishra ET. AL
References
1. Rorie DK, Muldoon SM, Krabill DR: Transient bundle branch
block occurring during anesthesia. Anesthesia Analgesia; 1972,
51:633-637.
2. Elderman DM, Hurlbert BJ: Intermittent left bundle branch block
during anesthesia. Anesthesia Analgesia; 1980, 59:628-630.
3. Domino KB, La Mantia KL, Geer RT, Klineberg PL: Intraoperative
diagnosis of rate-dependent bundle branch block. Can Anesth Soc J;
1984; 31:302-306.
4. Reyford H, De Groote P, Guermouche T, Boufflers E, Menu H,
Adnet P: Intermittent left bundle branch block revealed during
anaesthesia. British Journal of Anaesthesia; 1994, 72:700-701.
5. Tyagi A, Sethi AK, Agarwal V, Mohta M: Rate-dependent left
bundle branch block during anaesthesia. Anaesthesia and Intensive
Care; 2004, 32:715-718.
6. Littmann L, Symnaski JD: Hemodynamic complications of left
bundle branch block. J Electrocardiology; 2000, 33 suppl: 115-121.
7. Grady TA, Chiu AC, Snader CE, et al: Prognostic significance of
exercise- induced left bundle branch block. JAMA; 1998, 279:153156.
8. Fahy GJ, Pinski SL, Miller DP, et al: Natural history of isolated
bundle branch block. American Journal of Cardiology; 1996;
77:1185-1190.
9. Intraventricular Conduction defects. In: Wagner GS, ed. Marriott’s
Practical Electrocardiography. Lipincott Williams & Wilkins,
Philadelphia, 2001, 96-116.
10.Bauer GE. Transient Bundle branch Block. Circulation; 1964,
29:730-738.
11.Josephson ME: Intraventricular conduction disturbances. In:
Clinical Cardiac Electrophysiology: Techniques and Interpretations.
Lipincott Williams & Wilkins, Philadelphia, 2001, 110-139.
12.Rajesh, Bhoi S, Kumar M, Sharma B, Gupta BB. Rate dependent
left bundle branch block with chest pain in a 38 year old female. J
Ind Acad Clin Med; 2002, 3:193-194.
13.Wallace AG, Laszlo J: Mechanism influencing conduction in a case
of intermittent bundle branch block. Am Heart J; 1961, 61:548-555.