Interventricular delay less than 20 milliseconds on body surface potential mapping identifies cardiac resynchronization therapy responders

Abstract

Sea temperature around the coast of Scotland rises from 7 °C in late winter to 12 °C in late summer. Recently, it was shown that the selectivity of trawl codend was poorer in late winter than it was in late summer. A change in water temperature is expected to affect the escape speed of fish, and therefore the selectivity of the gear. Four experiments carried out in this study showed the effect of this seasonal temperature change on the ability of haddock, Melanogrammus aeglefinus, to escape from a codend. A temperature increase from 7 to 12 °C changed the minimum twitch contraction time of the lateral muscle from 38.8 to 27.6 ms. This gives a maximum tail beat frequency of 12.78 Hz at 7 °C rising to 19.12 Hz at 12 °C. Escape reflexes of the fish were significantly slower at 7 °C than at 12 °C (P<0.001). The shortest time to complete first body bend (stage 1) was 40 ms at 7 °C and 20 ms at 12 °C. The mean time taken to complete stage 1 at 7 °C (63.9 ms, S.E. 1.2) was significantly (t-test, P<0.001) longer than at 12 °C (40.1 ms, S.E. 0.92). The mean time taken to complete the propulsive stroke (stage 2) of the fast start was significantly (t-test, P<0.001) longer at 7 °C (108.5 ms, S.E. 5.3) than at 12 °C (72.6 ms, S.E. 2.6). The maximum speed recorded while competitively swimming for food reward was 7.9 L s−1 at 7 °C and 12.5 L s−1 at 12 °C. The observed maximum tail beat frequency used by haddock when leaving the mesh of a codend escape panel changed from 12 to 25 Hz. The general underlying physiological effect of a temperature increase of 10 °C was to double the speed of the maximum swimming ability (Q10°C=2). The effect of a change of only 5 °C on the ability to manoeuvre out of codend selection devices is discussed.