Table 3.

The beat-to-beat variability of the RR interval in isolated, Langendorff-perfused, AV-blocked rabbit hearts

	n	SD	RMS	RMSSD	Instability	LTV	STV
First set of experiments
H2O
Baseline	8	53 ± 20	447 ± 65	92 ± 37	71 ± 35	21 ± 9	55 ± 24
Pretreat	8	36 ± 14	681 ± 147	44 ± 19	45 ± 21	26 ± 11	24 ± 12
Treat	8	174 ± 145	783 ± 197	191 ± 162	44 ± 21	105 ± 80	48 ± 32
DMSO
Baseline	8	63 ± 35	482 ± 67	81 ± 56	116 ± 68	37 ± 30	50 ± 38
Pretreat	8	385 ± 211	944 ± 258	492 ± 254	208 ± 66	260 ± 157	168 ± 69
Treat	8	135 ± 57	680 ± 174	143 ± 41	223 ± 91	119 ± 65	77 ± 23
DOF1
Baseline	8	42 ± 20	443 ± 24	72 ± 38	57 ± 36	17 ± 9	44 ± 25
Pretreat	8	117 ± 93	566 ± 88	171 ± 140	51 ± 35	52 ± 37	58 ± 46
Treat	8	398 ± 216	1057 ± 318	535 ± 313	166 ± 90	231 ± 94	149 ± 62
SEA + DOF
Baseline	8	151 ± 48	575 ± 29	251 ± 91	281 ± 85	68 ± 30	151 ± 56
Pretreat	8	52 ± 26	729 ± 137	34 ± 18	48 ± 21	45 ± 21	14 ± 7
Treat	8	429 ± 109*#	1251 ± 81	534 ± 152	350 ± 82#†	341 ± 90	244 ± 70
Second set of experiments
DOF2
Baseline	8	141 ± 54	541 ± 38	262 ± 99	232 ± 87	39 ± 34	165 ± 62
Pretreat	8	75 ± 43	590 ± 63	113 ± 79	102 ± 83	37 ± 18	65 ± 53
Treat	8	183 ± 49	706 ± 75	267 ± 76	202 ± 72	120 ± 33	125 ± 34
DOF + LID
Baseline	8	108 ± 40	574 ± 66	180 ± 81	169 ± 82	36 ± 11	112 ± 57
Pretreat	8	155 ± 107	892 ± 122	268 ± 208	279 ± 202	37 ± 30	171 ± 140
Treat	8	649 ± 321	1660 ± 716	1043 ± 505	588 ± 375	333 ± 175	519 ± 267
DOF + VER
Baseline	8	89 ± 54	530 ± 61	141 ± 85	112 ± 54	56 ± 44	77 ± 42
Pretreat	8	33 ± 16	970 ± 182	36 ± 17	35 ± 15	27 ± 13	12 ± 5
Treat	8	854 ± 3	1920 ± 342‡	1301 ± 540	11169 ± 495	540 ± 211	709 ± 304

The beat-to-beat RR variability parameters in the first set of experiments and in the second set of experiments. Group size is indicated by n.

Values shown are mean ± SEM.

^*P < 0.05 versus DMSO;

^#P < 0.05 versus H₂O;

^†P < 0.05 versus DOF1;

^‡P < 0.05 versus DOF2. For further details, see Figures 2 and 3 and Table 2.

AV, atrioventricular; DMSO, dimethyl sulphoxide; SD, the standard deviation of the measured 40 consecutive RR intervals (ms); RMS, the root mean square of the measured 40 consecutive RR intervals (ms). RMSSD, the root mean square of the successive difference of the RR intervals (ms); Instability, QT instability (ms); LTV, long-term variability of the QT intervals (ms); STV, short-term variability of the QT intervals (ms). DOF, dofetilide: LID, lidocaine; SEA, SEA 0400; VER, verapamil.