Does maladaptive cardiovagal modulation extend to gastric modulation in women with chronic pelvic pain?

Abstract

Background: Women with chronic pelvic pain (CPP) have poor cardiovagal modulation. It is unclear whether this finding reflects a broader abnormality across many systems such as gastro-vagal modulation.

Aim: To determine if maladaptive cardiovagal activity in females with CPP is accompanied by maladaptive gastric myoelectric activity.

Methods: A total of 36 health controls (HC) and 75 CPP underwent supine (10 min), then upright (tilted 70° head up; 30 min), and back to supine (10 min) positions. High-frequency heart rate variability (HF-HRV; 0.15-0.4 Hz) was measured as an index of cardiovagal activity. Cutaneous electrogastrography (EGG) assessed gastric myoelectric activity pre- and during-upright tilt. EGG measures from 16 HC and 31 CPP patients were available for analysis and included relative percentage of gastric activity within the normal (2-4 cpm) and tachygastria (4-10 cpm) ranges, plus ratio of normal/tachygastria.

Results: HF-HRV was lower in CPP individuals at all time points (each p < .05). CPP individuals showed lesser decrease in HF-HRV from supine to upright, and poorer HF-HRV recovery from upright back to supine (F[1, 106] = 4.62, p = .034). HC showed increase in tachygastria activity (t[15] = -2.09, p = .054) while the CPP group showed no change in tachygastria activity from pre-upright to upright (t[30] = -0.62, p = .537).

Conclusions: Individuals with CPP going from supine to upright demonstrate an impairment in both tachygastria and the parallel decrement in HRV. These results support the hypothesis of a generalized blunting in the physiological modulation in CPP individuals affecting both cardiovascular and gastric systems.

Keywords: chronic pelvic pain; electrogastrography; gastric myoelectrical activity; heart rate variability; vagal modulation.

Figure 1:. HF-HRV throughout the experiment stratified by group

Note: This figure depicts natural log-transformed (ln) high frequency heart rate variability (HF-HRV) throughout the experiment stratified by heathy controls (HC; solid line) and chronic pelvic pain (CPP; dotted line) groups. HF-HRV was lower in CPP individuals at all time points (each p < .05). CPP individuals also showed a lesser decrease in HF-HRV from pre-tilt supine to upright-tilt, and poorer HF-HRV recovery from upright-tilt back to post-tilt supine (quadratic trend), as compared to HC (F (1,106) = 4.62, r = .204, p =.034).

Figure 2:. LF-HRV throughout the experiment stratified by group

Note: This figure depicts natural log-transformed (ln) low frequency heart rate variability (LF-HRV) throughout the experiment stratified by heathy controls (HC; solid line) and chronic pelvic pain (CPP; dotted line) groups. ANOVA and preplanned contrasts showed no significant differences in patterns of LF-HRV throughout the experiment between groups.

Figure 3:. LF/HF Ratio throughout the experiment stratified by group

Note: This figure depicts the low-to-high frequency ratio (LF/HF ratio) throughout the experiment stratified by heathy controls (HC; solid line) and chronic pelvic pain (CPP; dotted line) groups. Compared to the HC group, CPP individuals also showed a significantly higher LF/HF ratio post-tilt supine (F (1,106) = 4.36, r = .198, p = .039); this effect was attenuated during pre-tilt supine (F (1,106) = 3.22, r = .171, p = .075), and not significant during upright (F (1,106) = 0.00, r = .000, p = .999). Preplanned contrasts showed no significant differences in patterns of the LF/HF ratio throughout the experiment between groups.

Figure 4:. Tachygastria from pre-to post-tilt

Note: This figure depicts natural log-transformed (ln) tachygastria activity (4 – 10 cpm) from pre-tilt supine to upright-tilt stratified by heathy controls (HC; solid line) and chronic pelvic pain (CPP; dotted line) groups. The HC group showed a significant linear increase in tachygastria from pre-tilt to upright-tilt (p = .034). In contrast, the CPP group showed no significant linear trend in tachygastria from supine to upright (p = .537). Significant p-values bolded.

Figure 5:. Normal gastria from pre-tilt supine to upright-tilt

Note: This figure depicts natural log-transformed (ln) normal gastria activity (2–4 cpm) from pre-tilt supine to upright-tilt stratified by heathy controls (HC; solid line) and chronic pelvic pain (CPP; dotted line) groups. No significant linear trends were found in either group (p > .05).

Figure 6:. Normal-/tachy-gastria from pre-to post-tilt

Note: This figure depicts natural log-transformed (ln) normal/tachygastria ratio from pre-tilt supine to upright-tilt stratified by heathy controls (HC; solid line) and chronic pelvic pain (CPP; dotted line) groups. No significant linear trends were found in either group (p > .05).