Tailored Therapies for Cardiogenic Shock in Hypertrophic Cardiomyopathy: Navigating Emerging Strategies

Hypertrophic cardiomyopathy (HCM) is a complex and heterogeneous cardiac disorder, often complicated by cardiogenic shock, a life-threatening condition marked by severe cardiac output failure. Managing cardiogenic shock in HCM patients presents unique challenges due to the distinct pathophysiology of the disease, which includes dynamic left ventricular outflow tract obstruction, diastolic dysfunction, and myocardial ischemia. This review discusses current and emerging therapeutic strategies tailored to address the complexities of HCM-associated cardiogenic shock and other diseases with similar pathophysiology that provoke left ventricular outflow tract obstruction. We explore the role of pharmacological interventions, including the use of vasopressors and inotropes, which are crucial in stabilizing hemodynamics but require careful selection to avoid exacerbating the outflow obstruction. Additionally, the review highlights advancements in mechanical circulatory support devices such as extracorporeal membrane oxygenation (ECMO) and left ventricular assist devices (LVADs), which have become vital in the acute management of cardiogenic shock. These devices provide temporary support and bridge patients to recovery, definitive therapy, or heart transplantation, which remains a critical option for those with end-stage disease. Furthermore, the review delves into the latest research and clinical trials that are refining these therapeutic approaches, ensuring they are optimized for HCM patients. The impact of these treatments on patient outcomes, including survival rates and quality of life, is also critically assessed. In conclusion, this review underscores the importance of a tailored therapeutic approach in managing cardiogenic shock in HCM patients, integrating pharmacological and mechanical support strategies to improve outcomes in this high-risk population.

Effects of dopamine, norepinephrine or phenylephrine on the prevention of hypotension in isoflurane-anesthetized cats administered vatinoxan or vatinoxan and dexmedetomidine

OBJECTIVE

To determine the dose of phenylephrine, norepinephrine and dopamine necessary to maintain mean arterial pressure (MAP) within 70-80 mmHg during administration of isoflurane, isoflurane and vatinoxan and isoflurane, vatinoxan and dexmedetomidine at three plasma concentrations.

STUDY DESIGN

Randomized crossover experimental study.

ANIMALS

A group of five adult healthy neutered male cats.

METHODS

Instrumentation occurred during anesthesia with isoflurane in oxygen. Isoflurane end-tidal concentration was set to 1.25 × minimum alveolar concentration (MAC). Phenylephrine, norepinephrine or dopamine was administered to maintain MAP 70-80 mmHg. A target-controlled infusion system was used to administer vatinoxan at a target plasma concentration of 1 μg mL^-1 and three dexmedetomidine concentrations (5, 10 and 20 ng mL^-1). Isoflurane concentration was altered to maintain an equivalent 1.25 MAC. Heart rate, arterial blood pressure, central venous pressure, pulmonary artery pressure, pulmonary artery occlusion pressure, body temperature, arterial and mixed venous blood gas, cardiac output and drug concentrations were measured at baseline (isoflurane alone), during vatinoxan administration, and during administration of vatinoxan and dexmedetomidine at the three target concentrations.

RESULTS

MAP < 70 mmHg was observed with vatinoxan alone and in the dopamine treatment with dexmedetomidine concentrations ≤ 10 ng mL^-1. Norepinephrine and phenylephrine maintained MAP 70-80 mmHg during vatinoxan and dexmedetomidine ≤ 10 ng mL^-1. As the target dexmedetomidine concentration increased, the dose of norepinephrine and phenylephrine needed to maintain MAP 70-80 mmHg decreased; no treatment was necessary to maintain MAP > 70 mmHg at the 20 ng mL^-1 target dexmedetomidine concentration in most cats.

CONCLUSIONS AND CLINICAL RELEVANCE

Norepinephrine and phenylephrine, but not dopamine, are effective to prevent hypotension in isoflurane-anesthetized cats administered dexmedetomidine and vatinoxan.

Fluid Resuscitation for Refractory Hypotension

Hypotension is a common occurrence, especially in anesthetized patients and in critical patients suffering from hypovolemia due to shock and sepsis. Hypotension can also occur in normovolemic animals, anesthetized or conscious, under conditions of vasodilation or decreased cardiac function. The main consequence of hypotension is decreased organ perfusion and tissue injury/dysfunction. In the human literature there is no consensus on what is the threshold value for hypotension, and ranges from < 80 to < 100 mmHg for systolic blood pressure and from < 50 to < 70 mmHg for mean arterial blood pressure have been referenced for intraoperative hypotension. In veterinary medicine, similar values are referenced, despite marked differences in normal arterial blood pressure between species and with respect to humans. Therapeutic intervention involves fluid therapy to normalize volemia and use of sympathomimetics to enhance cardiac function and regulate peripheral vascular resistance. Despite these therapeutic measures, there is a subset of patients that are seemingly refractory and exhibit persistent hypotension. This review covers the physiological aspects that govern arterial blood pressure control and blood flow to tissues/organs, the pathophysiological mechanisms involved in hypotension and refractory hypotension, and therapeutic considerations and expectations that include proper interpretation of cardiovascular parameters, fluid recommendations and therapy rates, use of sympathomimetics and vasopressors, and newer approaches derived from the human literature.

Sympathomimetics in veterinary species under anesthesia

Sympathomimetic drugs mimic the physiological action of the sympathetic nervous system through interaction with adrenergic receptors. These drugs are commonly used to provide cardiovascular support in many veterinary species. Despite their common use, the literature evaluating their effectiveness can be somewhat limited depending on the species. This review details the mechanism of action of various sympathomimetic drugs and summarizes the literature that is available describing the efficacy of these drugs and their use in anesthetized veterinary species.