Myocardial metabolism in toxin-induced heart failure and therapeutic implications

High-dose insulin should be used before vasopressors/inotropes in calcium-channel blocker toxicity

High-dose insulin (HDI) therapy with adapted glucose supplementation to maintain euglycaemia has been suggested to treat calcium-channel blocker (CCB) poisonings. Its underlying mechanisms of action are now well documented. We present a narrative review of the published experimental studies, case reports and experts' opinions to support the effectiveness and safety of HDI in the treatment of CCB poisoning. Our review strongly encourages the use of HDI as first-line therapy in CCB-poisoned patients in the presence of cardiovascular compromise, especially if cardiac function impairment has been diagnosed, before, but without delaying, the administration of vasopressors/inotropic drugs.

Metabolic remodeling in takotsubo syndrome

The heart requires a large and constant supply of energy that is mainly the result of an efficient metabolic machinery that converges on mitochondrial oxidative metabolism to maintain its continuous mechanical work. Perturbations in these metabolic processes may therefore affect energy generation and contractile function directly. Metabolism characteristics in takotsubo syndrome (TTS) reveals several metabolic alterations called metabolic remodeling, including the hyperactivity of sympathetic metabolism, derangements of substrate utilization, effector subcellular dysfunction and systemic metabolic disorders, ultimately contributing to the progression of the disease and the development of a persistent and long-term heart failure (HF) phenotype. In this review, we explore the current literature investigating the pathological metabolic alterations in TTS. Although the metabolic dysfunction in takotsubo hearts is initially recognized as a myocardial metabolic inflexibility, we suggest that the widespread alterations of systemic metabolism with complex interplay between the heart and peripheral tissues rather than just cardiometabolic disorders per se account for long-term maladaptive metabolic, functional and structural impairment under this condition. Therapeutic strategies with the recent evidence from small clinical and animal researches, especially for targeting substrate utilization and/or oxidative stress, might be promising tools to improve the outcome of patients with TTS beyond that achieved with traditional sympathetic inhibition and symptomatic therapies.

A randomized controlled study comparing high-dose insulin to vasopressors or combination therapy in a porcine model of refractory propranolol-induced cardiogenic shock

Context: Although cerebral perfusion (CP) is preserved across a wide range of mean arterial pressures (MAP) through cerebral-vascular autoregulation, the relationship between MAP and CP in refractory poison-induced cardiogenic shock (PICS) has never been studied. We compared the effects of therapies used in PICS: high-dose insulin (HDI), HDI plus norepinephrine (NE), and vasopressors alone (NE plus epinephrine (Epi)) on cerebral tissue oxygenation (P_tO₂). Methods: Fifteen swine were randomized to either HDI, HDI + NE, or NE + Epi. All animals received a propranolol infusion using an established model of toxicity. At primary toxicity (P₁), defined as a 25% reduction in heart rate (HR) multiplied by MAP, the HDI and HDI + NE groups received HDI and the NE + Epi group received NE. Once a sustained MAP < 55 mmHg was reached (P₂), the HDI group received saline (NS), the HDI + NE group received NE and the NE + Epi group received Epi until death or censoring. P_tO₂ and hemodynamic parameters including MAP, cardiac output (CO) and central venous pressure (CVP) were measured every 10 minutes. Glucose and potassium were measured at predetermined intervals. Results: Animals treated with HDI + NE maintained P_tO₂ over time more than the HDI-alone group. Due to rapid hemodynamic collapse, we were unable to analyze P_tO₂ data in the vasopressor only animals. Mean survival time was 1.9, 2.9 and 0.1 hours for the HDI, HDI + NE and NE + Epi groups, respectively. Survival time from P₂ (sustained MAP <55 mmHg) to death or censoring was not different between HDI and HDI + NE groups. Conclusions: HDI + NE treatment was superior to HDI-alone at preserving P_tO₂ when MAP < 55 mmHg. We were unable to compare the P_tO₂ between the NE + Epi to the HDI or HDI + NE due to rapid decline in CO and death. If MAP is sustained at < 55 mmHg after maximizing HDI, adjunctive treatment with NE should be considered to preserve P_tO₂.