Table 2.

ECGs and perfused heart electrophysiology

Parameter	Wild type (n)	Scn5a+/− (n)	Significance
ECGs*
RR interval, ms	177  ± 38 (9)	193  ± 37 (9)	NS
P wave duration, ms	19  ± 3 (8)	24  ± 6 (9)	P < 0.05
PR interval, ms	41  ± 4 (9)	56  ± 6 (9)	P < 0.001
QT interval, ms	45  ± 5 (9)	49  ± 7 (9)	NS
Intact Langendorff-perfused hearts
Cycle length, ms	123  ± 5 (9)¶	420  ± 47 (6)	P < 0.001
Atrioventricular nodal refractory period, ms†	42  ± 3 (4)	69  ± 4 (4)	P < 0.001
Perfused ventricular preparations
Cycle length, ms	248  ± 23 (8)¶	No cardiac activity
Stimulus-response latency, ms‡	9  ± 1 (9)	18  ± 1 (6)	P < 0.001
Complex duration, ms‡	32  ± 3 (9)	64  ± 2 (6)	P < 0.001
Ventricular effective refractory period, ms§	29  ± 1 (9)	56  ± 7 (6)	P < 0.001

^¶, P < 0.001 comparing atria present and atria absent. All data are expressed as means ± SD. Statistical comparisons used Student's t test with P < 0.05 considered significant. n in all cases refers to the use of different preparations. NS, not significant. See Materials and Methods for details of ECG intervals. 

^† Point of failure of atrioventricular conduction during atrial pacing (see text and Materials and Methods for detail). 

^‡ Stimulus-to-response latency and complex duration measured during constant pacing (S1-S1) at a cycle length of 100 ms. 

^§ Ventricular effective refractory period obtained during decremental stimulation runs with initial stimulus interval (S1-S2) of 99 ms (see Fig. 4D). The ventricular effective refractory period is the longest S1-S2 that does not produce a propagated response.