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Changes in Q‐T and Q‐aT Intervals at Rest and During Exercise With Different Modes of Cardiac Pacing
Author(s) -
HEDMAN ANDERS,
NORDLANDER ROLF,
PEHRSSON S. KENNETH
Publication year - 1985
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.1985.tb05901.x
Subject(s) - medicine , qrs complex , cardiology , ventricular pacing , heart rate , cardiac pacing , rest (music) , atrioventricular block , heart failure , blood pressure
The influence of heart rate variation on the Q‐T and Q‐aT intervals (measured from the onset of the QRS to the end or the apex, respectively, of the T‐wave) was studied both at rest and during exercise using different modes of pacing. The studies were made on 21 patients with high‐degree atrioventricular block. In seven patients with programmable ventricular inhibited (VVI) pacemakers, an increase in pacing rate during rest produced significant shortening of both Q‐T and Q‐aT. During observations made at rest and during exercise in 14 patients with fixed rate VVI, atrial rate matched asynchronous (VVIm) or atrial triggered (VAT) pacing. Significant shortening of Q‐T and Q‐aT intervals occurred during exercise in all pacing modes, but was greatest with VVIm and VAT. The Q‐T and Q‐aT changes were almost parallel in all situations. For measurements made by two independent observers the coefficient of variation was lower for Q‐aT than for Q‐T (2.2 versus 2.5) and the correlation coefficient was higher (0.96 versus 0.93), indicating easier identification of Q‐aT than of Q‐T. This study indicated that changes in Q‐T and in Q‐aT are influenced by intrinsic factors in addition to the ventricular rate. Atrioventricular synchronization did not seem to influence these changes.