Cardiac Failure and Cardiogenic Shock: Insights Into Pathophysiology, Classification, and Hemodynamic Assessment

Abstract

Heart failure is defined as increased intracardiac pressures, either alone or combined with reduced cardiac output. Clinically, it is presented with signs and symptoms of congestion and compensated perfusion. Cardiogenic shock, on the other hand, is the spectrum of hemodynamic disturbances that lead to hypoperfusion or need for circulatory support, due to cardiac disease. Both entities affect millions of people worldwide, have a dismal prognosis, and constitute a severe socioeconomic burden. Heart failure can be the aftermath of ischemic heart disease, hypertension, arrhythmias, or cardiomyopathies. It undergoes multiple classifications, facilitating its investigation and treatment. The pathogenetic mechanisms differ in various types of heart failure, regarding the affected ventricles, the duration of symptoms, and their primary/secondary onset. These mechanisms reflect the complex interactions between cardiopulmonary, vascular, and hepatorenal systems. Acute deterioration of cardiac function can lead to cardiogenic shock. Myocardial infarction accounts for 81% of such cases. Healthy lifestyle and timely management of coronary artery disease are paramount, as they can prevent this life-threatening situation and reduce mortality and the economic burden for healthcare systems. Irrespective of the etiology, cardiogenic shock is interpreted using the pressure-volume loop. This can be modified for each ventricle, the underlying pathophysiology, and the time since symptoms' onset. It therefore provides valuable information about the native circulation and the expected alterations under mechanical or pharmacological support, facilitating the decision-making progress. In 2019, given the phenotypical heterogeneity of cardiogenic shock, the Society for Cardiovascular Angiography and Interventions introduced a classification system. According to this, patients are stratified in five stages proportionally to the severity of their condition. Aside from this classification, various biochemical, imaging, and hemodynamic monitoring indices are used to assess coagulation pathway and cardiac, hepatorenal, and pulmonary function, enabling the heart team to tailor therapy. Additionally, the prognostication progress is facilitated by scores, such as the Observatoire Regional Breton sur l'Infarctus (ORBI) score, the intra-aortic balloon pump (IABP) SHOCK-II score, and the CardShock score, indicating suitable escalation or de-escalation strategies. Despite the current progress, there are several areas of advancement regarding the role of vasoactive drugs in cardiogenic shock, revascularization options, mechanical ventilation patterns, hypothermia treatment, and mechanical circulatory support protocols.

Keywords: acute heart failure; cardiogenic shock; hemodynamics; left heart failure; pressure-volume loop; right heart failure.

Figure 1. Pressure-volume loops and relations in normal cardiac function

Reference: [73]; reprinted with permission Ea: arterial elastance; EDPVR: end-diastolic pressure-volume relationship; EDV: end-diastolic volume; Ees: end-systolic elastance; ESPVR: end-systolic pressure-volume relationship; ESV: end-systolic volume; HR: heart rate; LV: left ventricular; TPR: total peripheral resistance

Figure 2. LV pressure-volume loop in normal cardiac function (A) in comparison to the acute phase of myocardial infarction (B) and to CS (C)

Reference: [74]; reprinted with permission LV: left ventricular; Ea: arterial elastance; Emax: maximal elastance; LVEDP: left ventricular end-diastolic pressure; LVSP: left ventricular systolic pressure; SV: stroke volume; CS: cardiogenic shock

Figure 3. Pressure-volume loop of the RV in normal cardiac function

Reference: [82]; reprinted with permission Ea: arterial elastance; EDPVR: end-diastolic pressure-volume relationship; Ees: end-systolic elastance; ESPVR: end-systolic pressure-volume relationship; RV: right ventricular; RVEDP: right ventricular end-diastolic pressure; RVESP: right ventricular end-systolic pressure