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Ebstein, German physician, (1836-1912)
2 Mobitz' block type I and II: Second degree atrioventricular block in which progressive PR interval prolongation
precede a nonconducted P wave.(type I), and in which the PR interval remains unchanged prior to the P wave that
suddenly fails to conduct to the ventricles After Woldemar Mobitz, Russian-German cardiologist (1889-1951).
ICAO Preliminary Unedited Version — October 2008 III-1-27
particularly if the mean frontal QRS axis is abnormal, raises the possibility of distal conducting tissue
disease.
In the absence of such a complication an aviator may be certificated without restriction.
Second degree atrioventricular block is much less common than the first degree form in those of pilot age.
It was seen in only 4 (~0.003 per cent) of the 122 043 aviator ECGs reviewed in a Contracting State in
1962. Short periodicity (i.e. 2 : 3 and 3 : 4) Mobitz type I atrio-ventricular block, in which the PR interval
progressively prolongs until there is a non-conducted P wave, is sometimes seen during sleep in normal
young, especially athletic, individuals. It appears to carry no special risk and represents delayed
conduction at the level of the atrioventricular node which is of vagal origin. The coexistence of a bundle
branch disturbance will raise the possibility of distal conducting tissue (His-Purkinje) disease.
Mobitz type I atrioventricular block is very uncommon in normal subjects during the day and should
provoke investigation with 24-hour ambulatory monitoring and an exercise recording. In such cases, long
term follow-up is necessary, and a multi-crew (OML) restriction is required on the medical certificate.
The additional presence of an abnormal electrical axis and/or bundle branch disturbance is likely to
disbar.
More commonly, although not exclusively, Mobitz type II and 2 : 1 atrioventricular blocks represent delay
in the His-Purkinje network1 and carry a risk of progression to complete atrioventricular block with risk
of syncope.
Such abnormalities should lead to a denial of medical certification.
Complete (third degree) atrioventricular block disbars from all classes of medical certification. Provided
that there is no other disqualifying pathology and an endocardial pacemaker has been inserted, limited
Class 2 certification may be possible. Pacemaker dependence normally disqualifies from Class 1
operations. Congenital complete atrioventricular block is rare and although survival to middle years and
beyond is the rule, there is an excess risk of sudden cardiac death.
Mobitz type II, 2:1 atrioventricular block and complete atrioventricular block are inconsistent with any
class of medical certification.
INTRAVENTRICULAR CONDUCTION DISTURBANCES
Right bundle branch block
Incomplete right bundle branch block is a common anomaly that carries a normal prognosis in otherwise
normal subjects. It is seen in one to three per cent of professional aircrew. No special precautions are
needed. If there is significant right axis deviation, then the possibility of a secundum atrial septal defect
should be considered. See Appendix 1b: 15. Complete right bundle branch block is present in 0.2 per cent
of pilot applicants. It is characterized by a QRS width >120ms, with significant S waves in SI, V5 and
V6. There will be an rSR pattern in V1 and V2. See Appendix 1b: 16. Established complete right bundle
branch block appears to carry no adverse risk in asymptomatic and otherwise normal males of aircrew
age. It is seen in one per cent of professional aircrew. Even if it is newly acquired, the risk of a
cardiovascular event is likely to be minimal unless the block is the result of anteroseptal infarction. On
first presentation, applicants should undergo cardiological review including:
1 His-Purkinje network: a portion of the conducting system of the heart, beginning with the bundle of His and
ending at the terminus of the Purkinje fiber network within the ventricles. After W. His, Jr., Swiss physician (1863-
1934) and Johannes E. Purkinje, Czech physiologist (1787-1869)
ICAO Preliminary Unedited Version — October 2008 III-1-28
• exercise ECG (to at least three stages of the Bruce protocol)- satisfactorily achieved
• Holter monitoring – no significant rhythm or conduction disturbance
• echocardiography – no significant structural or functional abnormality of the heart
• electrophysiological study, if indicated, and/or coronary angiography, if indicated
The medical certificate should be restricted to multi-crew operation, if acquired >age 40 years:
if acquired < age 40 years, no restriction is necessary.
Satisfactory cardiological review at 12 months will usually permit unrestricted certification in those > 40
　
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