Download Intermittent Left Anterior Hemiblock during Treadmill Exercise Test*

Intermittent Left Anterior Hemiblock during
Treadmill Exercise Test*
Correlation with Coronary Arteriogram
Lt Col Rene A. Oliueros, MC, USAF; Capt John S e a w d h , MC, USAF;
Capt Frederick L. Weilund, MC, USAF; and
Maj Charles A. Boucher, MC, USAF
Two patients in whom left anterior hemiblock occurred
during a treadmill exercise test were found at cardiac
catheterhation to have significant obstruction of the
proximal portion of the left anterior descending coronary artery. After successfal myomdial revascuhuization
in one of these patients, a distorbme in conduction no
longer appeared during treadmill testing. To our knowledge, this association has not been previously reported,
and thii finding may be a useful clinical marker for
signEcant obetrncfive disease of the proximal portion of
the left anterior descending coronary artery.
he clinical sienlficance of ST-T abnormalities
during exercise is widely appreciated; however,
little attention has been given to the development
of defects in intraventricular conduction during exercise-induced ischemia. The purpose of this report
is to describe the occurrence of transient left anterior fascicular block (left anterior hemiblock)
with ischemia during a treadmill exercise test in
two patients with proven coronary artery disease
who had a high degree of obstruction in the proximal portion of the left anterior descending coronary
artery. To our knowledge, this association has not
been previously described.
the third minute of recovery at a heart rate of 75 beats per
minute. The left anterior hemiblock persisted up to the fifth
minute of recovery, when normal conduction returned.
At cardiac catheterization the patient had a resting left
ventricular end-diastolic pressure of 12 mm Hg, normal motion of the left ventricular wall, and the ejection fraction was
0.75. Coronary arteriograph studies revealed a 95 percent
stenosis of the left anterior descending coronary artery before
the first septa1 and first diagonal branches ( Fig 2 ) .
The patient subsequently underwent a saphenous vein
bypass graft to the left anterior descending coronary artery.
His postoperative course was uneventful, and a repeat study
two weeks later revealed the venous graft to be patent,
with good runoff. A treadmill stress test limited to six
minutes, which was performed two weeks after surgery, revealed no chest pain, no ST-segment depression, and no evidence of left anterior hemiblock or left bundle-branch block
after achieving a heart rate of 125 beats per minute (Fig l b ) .
A 41-year-old white man with an 11-month history of
angina pectoris refractory to medical therapy was referred
for further evaluation. He had no history of previous myocardial infarction. His coronary risk factors included obesity,
45 pack-years of smoking, and type 2-A hyperlipoproteinemia. The patient's blood pressure was 120/80 mm Hg; and
the findings from the rest of the physical examination, the
chest x-ray film, and the vectorcardiogram were normal. His
resting electrocardiogram showed right axis deviation.
The patient underwent a treadmill exercise test using
the protocol of Bruce et al.1 After four minutes of exercise,
the patient developed 3 mm of horizontal ST-segment depression in lead V, (Fig l a ) ; and at this time, the presence
of left anterior hemiblock was noted. During the following
minute, he developed chest pain, left bundle branch block,
and hypotension and the exercise test was terminated. The
patient's maximal heart rate was 115 beats per minute. The
left bundle-branch block reverted to left anterior hemiblock in
'From the Cardiology Service, Department of Medicine,
Wilford Hall USAF Medical Center, Lackland Air Force
Base, Texas.
Manuscript received February 14; revision accepted March 1
Reptint requests: Dr. Oliueros, USAF Hospital, Lackland
AFB, Texas 78236
A 37-year-old white man was admitted to our coronary
care unit with a twoday history of new unstable angina
pectoris. His only coronary risk factor was a 30 pack-year
history of smoking. The patient's blood pressure was 140/80
mm Hg, and the findings from the rest of his physical examination were normal. His chest x-ray film was normal,
and his ECG showed T-wave inversion in leads V , and
Ve. Serial determinations of serum enzymes and serial ECGs
revealed no evidence of myocardial infarction.
The patient underwent a treadmill exercise test a week
later using the United States Air Force SAM protocol.2 He
developed left anterior hemiblock at the sixth minute of
exercise at a heart rate of 166 beats per minute, accompanied by 1 mm of ST-segment elevation in leads 1 and
aVL (Fig 3), but he did not complain of chest pain.
The patient's exercise test was terminated because of these
electrocardiographic changes and because 90 percent of the
maximal predicted heart rate had already been achieved.
The left anterior hemiblock disappeared after two minutes
of recovery, when the heart rate was 136 beats per minute
(Fig 3 ) , and the ST-segment elevation resolved. Ischemic
ST-segment depression of 1 mm was noted in lead V, at the
sixth minute of recovery.
CHEST, 72: 4, OCTOBER, 1977
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FIGURE1. ECGS from patient 1. la, Left
anterior hemiblock developed at fourth minute of exercise, accompanied by electrocardiographic signs of myocardial ischemia. lb,
After successful myocardial revascularization. Patient was exercised to comparable
heart rate, but no abnormality of conduction
was noted.
On cardiac catheterization the patient's left ventricular
end-diastolic pressure was 10 mm Hg, no abnormalities of
wall motion were noted on left ventriculographic studies,
and the ejection fraction was 0.60. On coronary arteriographic studies, the patient had a 60 percent stenosis of
the proximal portion of the left anterior descending coronary artery before the origin of the major septal branch and
80 percent stenosis of the first diagonal branch. The lesion
of the left anterior descending coronary artery could be
visualized only on the half axial projection (Fig 4).3 The
patient was completely free of angina and was discharged
on medical therapy.
FIGURE2. Injection of contrast material into left coronary
artery in patient 1shows 95 percent stenosis of proximal portion of left anterior descending coronary artery.
CHEST, 72: 4, OCTOBER, 1977
The electrocardiographic criteria for the diagnosis of left anterior hemiblock have been described
by Rosenbaum et a14 and consist of left axis deviation of -45' or more in the frontal plane, small
Q waves in leads 1 and aVL, and an rS pattern in
leads 2,3, and aVF. Intermittent left anterior hemiblock has been described under different clinical
conditions as shock, hypertension, and congestive
heart failure.5 It has also been described after the
injection of angiographic contrast material into the
left coronary arterial system of patients with normal
coronary arteries, as well as in the presence of coronary arterial disea~e.~
There is one isolated report of
intermittent left anterior hemiblock occurring only
during tachycardia (phase 3, left anterior hemiblock) in a patient with muscular dystrophy.'
The occurrence of left anterior hemiblock during
exercise-induced ischemia has not previously been
reported, to our knowledge, and Ellestada did not
see a single instance after performing 3,500 exercise
tests. After exercising 29 patients with isolated obstruction of the left anterior descending coronary
artery, Goldschlager et ale concluded that there was
no characteristic response on treadmill testing that
could identify such a lesion. Theye did not mention
INTERMITTENT LEFT ANTERIOR HEMIBLOCK 493
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FIGURE
4. Left coronary arteriogram obtained in patient 2
in half axial projection. Lesion in proximal portion of left
anterior descending coronary artery is evident.
test, more cases of intermittent left anterior hemiblock could be observed.
Although our observation needs confirmation
from a large series of patients, we conclude that
the occurrence of left anterior hemiblock during
exercise-induced ischemia is unusual but, when
present, probably is a reliable indicator of disease
in the proximal portion of the left anterior descending coronary artery.
ACKNOWLEDGMENTS: We are indebted to Dr. Charles
H. Bechann, Victor F. Froelicher, and Michael J. Gordon for
reviewin this manuscript. We would also like to thank SS
Aida ~ n f r e w sfor technical help and Ms. Mary Lou R i d
son for secretarial support.
FIGURE3. ECGS from patient 2. Left anterior hemiblock
developed at seventh minute of exercise, accompanied by
ST-segment elevation in leads 1 and aVL.
whether the obstruction of the left anterior descending coronary artery was proximal or distal to
the origin of the major septal artery. Our data, although limited by the small number of patients,
seems to indicate that intermittent left anterior
hemiblock during exercise, associated with electrocardiographic evidence of myocardial ischemia,
may be used as a marker for severe disease of the
proximal portion of the left anterior descending
coronary artery before the origin of the major septal
branch. Before and after surgery, we subjected our
first patient to stress testing until comparable heart
rates were achieved, and the absence of any defect
of intraventricular conduction after surgery seems
to indicate that the left anterior hemiblock was a
manifestation of septal ischemia, rather than a raterelated phenomenon.
Standard limb leads are essential for the diagnosis of left anterior hemiblock. If the standard limb
leads, as well as the precordial leads, are recorded
routinely during the performance of an exercise
REFERENCES
Bruce RA, Blackmon JR, Jones JW, et al: Exercise testing
in adult normal subjects and cardiac patients. Pediatrics
'suppl 1) :742, 1963
2 Froelicher F: Use of the Exercise Electrocardiogram to
Identify Latent Coronary Atherosclerotic Heart Disease
(report SAM TR 7826). United States Air Force, 1976
3 Bumell IL, Green DG,Tandon RN, et a]: The half axial
projection: A new look at the proximal left coronary
artery. Circulation 48: 1151-1156, 1973
4 Rosenbaum M: The hemiblocks: Diagnostic criteria and
clinical significance. Mod Concepts Cardiovasc Dis 39:
141-146, 1970
5 Rosenbaum MB, Elizari MV, Levi RJ, et al: Five cases
of intermittent left anterior hemiblock. Am J Cardiol
24: 1-7, 1969
6 Fernandez F, &bat L, Lenegre J: Electrocardiographic
study of left intraventricular hemiblock in man during
selective coronary arteiography. Am J Cardiol 26:105,
1970
7 Elizari MV, L&zari JO, Rosenbaum MB: Phase-3 and
phase-4 intermittent left anterior hemiblock: Report of
the first case in the literature. Chest 62373-677, 1972
8 Ellestad MH: Stress Testing. Philadelphia, FA Davis Co,
1975, p 132
9 Goldschlager N, Selzer A, Cohn K: Treadmill stress test
as indicator of presence and severity of coronary artery
disease. AM Intern Med 85277-286, 1976
CHEST, 72: 4, OCTOBER, 1977
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