Cardiogenic shock: Basics and clinical considerations

Validation of a Multiscale Computational Model Using a Mock Circulatory Loop to Simulate Cardiogenic Shock

The objectives of this study are to characterize the hemodynamics of cardiogenic shock (CS) through a computational model validated using a mock circulatory loop (MCL) and to perform sensitivity analysis and uncertainty propagation studies after the American Society of Mechanical Engineers (ASME) Validation and Verification (V&V) guidelines. The uncertainties in cardiac cycle time ( ), total resistance ( ), and total volume ( ) were quantified in the MCL and propagated in the computational model. Both models were used to quantify the pressure in the left atrium, aorta (Ao), and left ventricle (LV), along with the flow through the aortic valve, reaching a good agreement. The results suggest that 1) is the main source of uncertainty in the variables under study, 2) showed its greatest impact on the uncertainty of Ao hemodynamics, and 3) mostly affected the uncertainty of LV pressure and Ao flow at the late-systolic phase. Comparison of uncertainty levels in the computational and experimental results was used to infer the presence of additional contributing factors that were not captured and propagated during a first analysis. Future work will expand upon this study to analyze the impact of mechanical circulatory support devices, such as ventricular assist devices, under CS conditions.

Myocardial stretch-induced compliance is abrogated under ischemic conditions and restored by cGMP/PKG-related pathways

Introduction: Management of acute myocardial infarction (MI) mandates careful optimization of volemia, which can be challenging due to the inherent risk of congestion. Increased myocardial compliance in response to stretching, known as stretch-induced compliance (SIC), has been recently characterized and partly ascribed to cGMP/cGMP-dependent protein kinase (PKG)-related pathways. We hypothesized that SIC would be impaired in MI but restored by activation of PKG, thereby enabling a better response to volume loading in MI. Methods: We conducted experiments in ex vivo rabbit right ventricular papillary muscles under ischemic and non-ischemic conditions as well as pressure-volume hemodynamic evaluations in experimental in vivo MI induced by left anterior descending artery ligation in rats. Results: Acutely stretching muscles ex vivo yielded increased compliance over the next 15 min, but not under ischemic conditions. PKG agonists, but not PKC agonists, were able to partially restore SIC in ischemic muscles. A similar effect was observed with phosphodiesterase-5 inhibitor (PDE5i) sildenafil, which was amplified by joint B-type natriuretic peptide or nitric oxide donor administration. In vivo translation revealed that volume loading after MI only increased cardiac output in rats infused with PDE5i. Contrarily to vehicle, sildenafil-treated rats showed a clear increase in myocardial compliance upon volume loading. Discussion: Our results suggest that ischemia impairs the adaptive myocardial response to acute stretching and that this may be partly prevented by pharmacological manipulation of the cGMP/PKG pathway, namely, with PDE5i. Further studies are warranted to further elucidate the potential of this intervention in the clinical setting of acute myocardial ischemia.

Hemodynamics of Cardiogenic Shock

Cardiogenic shock (CS) represents an advanced state of morbidity along the pathophysiologic pathway of end-organ hypoperfusion caused by reduced cardiac output and blood pressure. Acute coronary syndromes remain the most common cause of CS. The spectrum of hypoperfusion states caused by low cardiac output ranges from pre-CS to refractory CS and can be characterized by an array of hemodynamic parameters. This review provides the foundation for a hemodynamic understanding of CS including the use of hemodynamic monitoring for diagnosis and treatment, the cardiac and vascular determinants of CS, and a hemodynamic approach to risk stratification and management of CS.

Predictive value of the baseline electrocardiogram ST-segment pattern in cardiogenic shock: Results from the CardShock Study

BACKGROUND

The most common aetiology of cardiogenic shock (CS) is acute coronary syndrome (ACS), but even up to 20%-50% of CS is caused by other disorders. ST-segment deviations in the electrocardiogram (ECG) have been investigated in patients with ACS-related CS, but not in those with other CS aetiologies. We set out to explore the prevalence of different ST-segment patterns and their associations with the CS aetiology, clinical findings and 90-day mortality.

METHODS

We analysed the baseline ECG of 196 patients who were included in a multinational prospective study of CS. The patients were divided into 3 groups: (a) ST-segment elevation (STE). (b) ST-segment depression (STDEP). (c) No ST-segment deviation or ST-segment impossible to analyse (NSTD). A subgroup analysis of the ACS patients was conducted.

RESULTS

ST-segment deviations were present in 80% of the patients: 52% had STE and 29% had STDEP. STE was associated with the ACS aetiology, but one-fourth of the STDEP patients had aetiology other than ACS. The overall 90-day mortality was 41%: in STE 47%, STDEP 36% and NSTD 33%. In the multivariate mortality analysis, only STE predicted mortality (HR 1.74, CI₉₅ 1.07-2.84). In the ACS subgroup, the patients were equally effectively revascularized, and no differences in the survival were noted between the study groups.

CONCLUSION

ST-segment elevation is associated with the ACS aetiology and high mortality in the unselected CS population. If STE is not present, other aetiologies must be considered. When effectively revascularized, the prognosis is similar regardless of the ST-segment pattern in ACS-related CS.

Strong-ion gap approach in patients with cardiogenic shock following ST-elevation myocardial infarction

OBJECTIVE

Assess if acid-base evaluation by Stewart's approach had a clinical role in cardiogenic shock (CS) following ST-elevation myocardial infarction (STEMI).

SETTING

There are three widely used approaches to investigate metabolic acidosis: base excess (BE), anion gap (AG) and the Stewart's approach or strong ion gap (SIG). Available studies suggest the usefulness of SIG in sepsis and trauma. No data are so far available in CS.

MEASUREMENTS AND RESULTS

We enrolled 63 consecutive patients with CS following STEMI submitted to Percutaneous Coronary Intervention (PCI). On admission, the APACHE II (Acute physiology and chronic health evaluation II) score and HOMA (Homeostasis model assessment) index were assessed together with glomerular filtration rate (eGFR), quantitative BE, AG, lactate values and 12 h lactate clearance. Non-survivors showed a higher incidence of PCI failure, higher APACHE II score, lower LVEF, lower eGFR, lower 12 h lactate clearance; a higher admission lactate and more negative BE. No difference was detectable in AG and SIG. Only 3 patients exhibited pathological values of SIG (≥ 2) and only 1 of these patients died.

CONCLUSIONS

According to our data the SIG approach does not seem to add further information to usual parameters in acid-base evaluation or early risk stratification in CS patients.

Heart failure while on ventricular assist device support: a true clinical entity?

Ventricular assist devices (VADs) have become an established therapeutic option for patients with end-stage heart failure. The appearance of heart failure in VAD patients seems unexpected. Nevertheless, this phenomenon is not rare. We report six cases of VAD patients with clinical presentation of heart failure at different times after implantation and describe the mechanisms involved. The aetiology of this heart failure, like its clinical presentation, varies and has yet to be identified.

The role of vasoactive agents in the resuscitation of microvascular perfusion and tissue oxygenation in critically ill patients

Purpose

The clinical use of vasoactive drugs is not only intended to improve systemic hemodynamic variables, but ultimately to attenuate derangements in organ perfusion and oxygenation during shock. This review aims (1) to discuss basic physiology with respect to manipulating vascular tone and its effect on the microcirculation, and (2) to provide an overview of available clinical data on the relation between vasoactive drugs and organ perfusion, with specific attention paid to recent developments that have enabled direct in vivo observation of the microcirculation and concepts that have originated from it.

Methods

A MedLine search was conducted for clinical articles in the English language over the last 15 years pertainig to shock, sepsis, organ failure, or critically ill patients in combination with vasoactive drugs and specific variables of organ perfusion/oxygenation (e.g., tonometry, indocyanine clearance, laser Doppler, and sidestream dark field imaging).

Results

Eighty original papers evaluating the specific relationship between organ perfusion/oxygenation and the use of vasoactive drugs were identified and are discussed in light of physiological theory of vasomotor tone.

Conclusions

Solid clinical data in support of the idea that increasing blood pressure in shock improves microcirculatory perfusion/oxygenation seem to be lacking, and such a concept might not be in line with physiological theory of microcirculation as a low-pressure vascular compartment. In septic shock no beneficial effect on microcirculatory perfusion above a mean arterial pressure of 65 mmHg has been reported, but a wide range in inter-individual effect seems to exist. Whether improvement of microcirculatory perfusion is associated with better patient outcome remains to be elucidated.

Human neutrophil peptides: a novel potential mediator of inflammatory cardiovascular diseases

The traditional view of atherosclerosis has recently been expanded from a predominantly lipid retentive disease to a coupling of inflammatory mechanisms and dyslipidemia. Studies have suggested a novel role for polymorphonuclear neutrophil (PMN)-dominant inflammation in the development of atherosclerosis. Human neutrophil peptides (HNPs), also known as alpha-defensins, are secreted and released from PMN granules upon activation and are conventionally involved in microbial killing. Current evidence suggests an important immunomodulative role for these peptides. HNP levels are markedly increased in inflammatory diseases including sepsis and acute coronary syndromes. They have been found within the intima of human atherosclerotic arteries, and their deposition in the skin correlates with the severity of coronary artery diseases. HNPs form complexes with LDL in solution and increase LDL binding to the endothelial surface. HNPs have also been shown to contribute to endothelial dysfunction, lipid metabolism disorder, and the inhibition of fibrinolysis. Given the emerging relationship between PMN-dominant inflammation and atherosclerosis, HNPs may serve as a link between them and as a biological marker and potential therapeutic target in cardiovascular diseases including coronary artery diseases and acute coronary syndromes.