Telemetric long-term assessment of autonomic function in experimental heart failure

Despite medical advances in the treatment of heart failure (HF), mortality remains high. It has been shown that alterations of the autonomic-nervous-system (ANS) are associated with HF progression and increased mortality. Preclinical models are required to evaluate the effectiveness of novel treatments modulating the autonomic imbalance. However, there are neither standard models nor diagnostic methods established to measure sympathetic and parasympathetic outflow continuously. Digital technologies might be a reliable tool for continuous assessment of autonomic function within experimental HF models. Telemetry devices and pacemakers were implanted in beagle dogs (n = 6). HF was induced by ventricular pacing. Cardiac hemodynamics, plasma catecholamines and parameter describing the ANS ((heart rate variability (HRV), deceleration capacity (DC), and baroreflex sensitivity (BRS)) were continuously measured at baseline, during HF conditions and during recovery phase. The pacing regime led to the expected depression in cardiac hemodynamics. Telemetric assessment of the ANS function showed a significant decrease in Total power, DC, and Heart rate recovery, whereas BRS was not significantly affected. In contrast, plasma catecholamines, revealing sympathetic activity, showed only a significant increase in the recovery phase. A precise diagnostic of the ANS in the context of HF is becoming increasingly important in experimental models. Up to now, these models have shown many limitations. Here we present the continuous assessment of the autonomic function in the progression of HF. We could demonstrate the advantage of highly resolved ANS measurement by HR and BP derived parameters due to early detection of an autonomic imbalance in the progression of HF.

"Digital biomarkers" in preclinical heart failure models - a further step towards improved translational research

Innovations in the development of novel heart failure therapies are essential to further increase the predictive value of early research findings. Animal models are still playing a pivotal role in 'translational research'. In recent years, the transferability from animal studies has been more and more critically discussed due to persistent high attrition rates in clinical trials. However, there is an increasing trend to implement mobile health devices in preclinical studies. These devices can increase the predictive value of animal models by providing more accurate and translatable data and protect from confounding factors. This review outlines the current prevalence and opportunities of these techniques in preclinical heart failure research studies to accelerate the integration of these important tools. A literature screening for preclinical heart failure studies in large animals implementing telemetry devices over the last decade was performed. Twelve out of 43 publications were included. A variety of different hemodynamic and cardiac parameters can be recorded in conscious state by means of telemetry devices in both, the animal model and the patient. The measurement quality is consistently rated as valid and robust. Mobile health technologies functioning as digital biomarkers represent a more predictive approach compared to the traditionally used invasive measurement techniques, due to the possibility of continuous data collection in the conscious animal. Furthermore, they help to implement the 3R concept (reduction, refinement, replacement) in animal research. Despite this, the use of these techniques in preclinical research has been restrained to date.

Longitudinal characterization of clinically relevant haemodynamics in conscious Ossabaw pigs with HFpEF

Background

The constantly growing population of patients suffering from heart failure with preserved ejection fraction (HFpEF) is one of the largest unmet needs in cardiovascular medicine and translational animal models are important for identification and profiling of novel therapeutic approaches. Large animal models have shown that chronic cardiac pressure overload by aortic banding (AoB), when combined with a Western diet leads to left ventricular hypertrophy, diastolic dysfunction and metabolic syndrome in the Ossabaw pig, reflecting important features of human HFpEF characteristics. However, the requirement of invasive diagnostics under anaesthesia often limits the ability to monitor disease development continuously and compromises the results. Therefore, current disease models lack the temporal progression of clinically relevant HFpEF parameters like the left ventricular end diastolic pressure (LVEDP) and time constant of left ventricular relaxation (Tau).

Purpose

We aim to non-invasively investigate disease progression in Ossabaw pigs exhibiting a cardiometabolic HFpEF phenotype. The longitudinal assessment of LVEDP, Tau and heart rate (HR) should identify a time window to test novel therapeutics.

Methods

Naive, female Ossabaw pigs were instrumented with telemetric devices followed by AoB to induce chronic cardiac pressure overload. The wound healing and acclimatization period was followed by the start of a Western diet feeding regime to mimic components of the metabolic syndrome. Disease progression was characterized over 9 months by monthly telemetric recordings of LVEDP, Tau and HR and compared to a control (Ctrl) measurement in healthy animals. All animal studies followed the `Principles of laboratory animal care'.

Results

Compared to Ctrl the LVEDP is significantly elevated already 1 month (+8.90±0.4 mmHg) after AoB and further increases over time until 8 months (+18.80±0.4 mmHg) post AoB. Significant elevations in Tau are evident 4 months (+1.61±0.4 ms) post AoB. After 1 month the HR is significantly elevated (+13.90±0.7 bpm) but tends to normalize between 5 to 7 months post AoB. After AoB a maximal relative increase in LVEDP (+5.12±0.4 mmHg), Tau (+5.04±0.4 ms) and HR (+16.90±0.7 bpm) can be observed after 8 months.

Conclusions

We present long term haemodynamic changes over time in a translational in vivo model for HFpEF in Ossabaw pigs with high temporal resolution. For the first time elevations in key parameters allow to set a time point where HFpEF characteristics are evident, and a drug testing regime could be started. The opportunity to non-invasively and longitudinally follow on LVEDP, Tau and HR will be a clear benefit in the development of novel treatment options for HFpEF.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Bayer AG, Wuppertal

sGC stimulation lowers elevated blood pressure in a new canine model of resistant hypertension

Therapy-resistant hypertension is a serious medical problem, causing end-organ damage, stroke, and heart failure if untreated. Since the standard of care fails in resistant hypertension patients, there is still a substantial unmet medical need for effective therapies. Active stimulation of soluble guanylyl cyclase via novel soluble guanylyl cyclase stimulators might provide an effective treatment option. To test this hypothesis, we established a new experimental dog model and investigated the effects of the soluble guanylyl cyclase-stimulator BAY 41-2272. In beagle dogs, a resistant hypertension phenotype was established by combining unilateral renal wrapping with the occlusion of the renal artery in the contralateral kidney. The most frequently used antihypertensive drugs were administered orally, either alone or in combination, and their acute effect on telemetric measured blood pressure was assessed and compared with that of BAY 41-2272. The chosen disease stimulus led to a moderate and stable increase in blood pressure. Even high doses of standard-of-care antihypertensives only slightly decreased blood pressure. In contrast, the administration of the soluble guanylyl cyclase stimulator BAY 41-2272 as standalone therapy led to a dose-dependent reduction in blood pressure (-14.1 ± 1.8 mmHg). Moreover, BAY 41-2272 could also further decrease blood pressure in addition to a triple combination of standard-of-care antihypertensives (-28.6 ± 13.2 mmHg). BAY 41-2272 was highly efficient as a standalone treatment in resistant hypertension but was also effective in addition to standard-of-care treatment. These data strongly suggest that soluble guanylyl cyclase stimulators might provide an effective pharmacologic therapy for patients with resistant hypertension.