Circadian rhythms in pump parameters of patients on contemporary left ventricular assist device support

BACKGROUND

Algorithms to monitor pump parameters are needed to further improve outcomes after left ventricular assist device (LVAD) implantation. Previous research showed a restored circadian rhythm in pump parameters in patients on HeartWare (HVAD) support. Circadian patterns in HeartMate3 (HM3) were not studied before, but this is important for the development of LVAD monitoring algorithms. Hence, we aimed to describe circadian patterns in HM3 parameters and their relation to patterns in heart rate (HR).

METHODS

18 HM3 patients were included in this study. HM3 data were retrieved at a high frequency (one sample per 1 or 2 h) for 1-2 weeks. HR was measured using a wearable biosensor. To study overall patterns in HM3 parameters and HR, a heatmap was created. A 24-h cosine was fitted on power and HR separately. The relationship between the amplitude of the fitted cosines of power and HR was calculated using Spearman correlation.

RESULTS

A lower between patient variability was found in power compared with flow and PI. 83% of the patients showed a significant circadian rhythmicity in power (p < 0.001-0.04), with a clear morning increase. All patients showed significant circadian rhythmicity in HR (p < 0.001-0.02). The amplitudes of the circadian rhythm in power and HR were not correlated (Spearman correlation of 0.32, p = 0.19).

CONCLUSIONS

A circadian rhythm of pump parameters is present in the majority of HM3 patients. Higher frequency pump parameter data should be collected, to enable early detection of complications in the future development of predictive algorithms.

Circadian dependence of the acute immune response to myocardial infarction

Aim

Circadian rhythms control many physiological processes, including numerous aspects of the immune system. Whether these immunological oscillations play a role in the pathophysiology after ischemic injury, such as myocardial infarction (MI), remains unclear. In this study, we aimed to characterize circadian rhythms during the acute inflammatory responses after MI.

Methods and results

Balb/c mice were operated at Zeitgeber Time (ZT) 2, 8, 14 and 20. Three hours after MI, animals were terminated and blood and hearts were collected to assess immunological status and damage. We observed diurnal fluctuation in leukocyte numbers in the blood, peaking during the rest-phase (ZT2 and 8) of the circadian cycle. Interestingly, the homing and infiltration of neutrophils to the injured myocardium was more pronounced during the active-phase of the mice (ZT14 and 20), at which time higher levels of Troponin-T were measured in the serum. Higher neutrophil extravasation during the active phase (especially the sleep-to-wake transition, ZT14) was also correlated to greater chemokine release in the blood and adhesion molecule expression in the heart.

Conclusion

The occurrence of a myocardial infarction during the early-morning hours leads to greater myocardial damage in patients. In the present study, we showed that the neutrophil response in the first hours after MI is stronger during the sleep-to-wake transition, thereby potentially playing a role in the worse clinical outcome observed during this time period.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): This research received funding from the EU's H2020 research and innovation programme under Marie S. Curie cofund RESCUE grant agreement No 801540.