Overcoming the Limits of Ejection Fraction and Ventricular-Arterial Coupling in Heart Failure

Effect of prior tuberculosis on cardiovascular status in perinatally HIV-1-infected adolescents

Whether, and how, co-occurring HIV-1 infection (HIV) and tuberculosis (TB) impact cardiovascular status, especially in adolescents with perinatally acquired HIV (APHIV), have not been examined. We hypothesized that APHIV with previous active TB have worse cardiac efficiency than APHIV without TB, which is mediated by increased inflammation. Arterial elastance (Ea) and ventricular end-systolic elastance (Ees) were assessed by cardiovascular magnetic resonance, and ventriculoarterial coupling (VAC) estimated as Ea/Ees ratio. Inflammation was measured by high sensitivity C-reactive protein (hsCRP). Previous TB in APHIV was associated with reduced cardiac efficiency, related to an altered ventriculoarterial coupling. However, we did not find evidence of hsCRP mediated effects in the association between prior TB and cardiac efficiency. The clinical significance of these findings requires further study, including a wider range of biomarkers of specific immune pathways.

Pulse Pressure is Sex-Specifically Associated with the Ratio of Diastolic and Systolic Arterial Pressure in Healthy Children, and Differently During Night Versus Daytime Recordings

Noninvasive blood pressure recordings typically focus on systolic blood pressure (SBP) and diastolic pressure (DBP). Derived metrics are often analyzed, e.g. pulse pressure (PP), defined as SBP minus DBP. As the metric PP is not unique, we introduced the PP companion (PPC), calculated using the Pythagorean theorem. PPC is associated with mean arterial pressure (MAP). Another mathematical construct frequently used in hemodynamic studies refers to the ratio of DBP and SBP, denoted as Prat. PP and Prat share the same companion (C). The association between PratC and MAP, as well as the connection between PP and Prat has not been studied in healthy children. We analyzed a large set of daytime (DT) and nighttime (NT) data (N=949, age 5 to 16 years, including 485 girls), published in the literature. Average PP increases with age (in 0.5 year increments), while Prat decreases. Prat vs PP yields R2>0.985 for both DT and NT data, when stratified for boys and girls. PPC is significantly lower (P<0.0001) during the night for both sexes. We conclude that Prat carries no substantial incremental value beyond PP, in contrast to PPC which points to DT/NT, age-dependent and sex-specific differences in these children.Clinical Relevance- Various derived metrics based on blood pressure have been introduced in hemodynamic studies, but not all of them are fully independent. The diastolic to systolic pressure ratio in healthy children is inversely associated with pulse pressure, showing partial sex-specific overlap, but substantial daytime versus night differences.

Hypercontractile Cardiac Phenotype in Mice with Migraine-Associated Mutation in the Na+,K+-ATPase α2-Isoform

Two α-isoforms of the Na⁺,K⁺-ATPase (α₁ and α₂) are expressed in the cardiovascular system, and it is unclear which isoform is the preferential regulator of contractility. Mice heterozygous for the familial hemiplegic migraine type 2 (FHM2) associated mutation in the α₂-isoform (G301R; α₂^+/G301R mice) have decreased expression of cardiac α₂-isoform but elevated expression of the α₁-isoform. We aimed to investigate the contribution of the α₂-isoform function to the cardiac phenotype of α₂^+/G301R hearts. We hypothesized that α₂^+/G301R hearts exhibit greater contractility due to reduced expression of cardiac α₂-isoform. Variables for contractility and relaxation of isolated hearts were assessed in the Langendorff system without and in the presence of ouabain (1 µM). Atrial pacing was performed to investigate rate-dependent changes. The α₂^+/G301R hearts displayed greater contractility than WT hearts during sinus rhythm, which was rate-dependent. The inotropic effect of ouabain was more augmented in α₂^+/G301R hearts than in WT hearts during sinus rhythm and atrial pacing. In conclusion, cardiac contractility was greater in α₂^+/G301R hearts than in WT hearts under resting conditions. The inotropic effect of ouabain was rate-independent and enhanced in α₂^+/G301R hearts, which was associated with increased systolic work.

The Ratio of Diastolic and Systolic Arterial Pressure is Associated with Pulse Pressure

Pulse pressure (PP) is defined as the difference between systolic blood pressure (SBP) and diastolic blood pressure (DBP). The metric PP is not unique, as numerous combinations of SBP and DBP yield the same value for PP. Therefore, we introduced the PP companion (PPC) which is calculated using the Pythagorean theorem. Only the combination of PP and PPC offers unique characterization. Interestingly, PPCwas found to be associated with mean arterial pressure (MAP). Another mathematical construct frequently used in hemodynamic studies refers to the ratio of DBP and SBP, or DBP/SBP, denoted as Prat. As Prat and PP share the same companion (C), we investigated the association between PratC and MAP, as well as the connection between PP and Prat. Various patient cohorts were included: A) 52 heart failure patients (16 women), B) 88 patients (11 women) with acute cardiac syndromes, C) 257 patients (68 men) diagnosed with atherosclerosis or any of various types of autoimmune disease, and D) 106 hypertensives (51 men). Linear regression analysis resulted in the following correlations: A: R (PratC, MAP) = 0.94, R (PP, Prat) = -0.91 B: R (PratC, MAP) = 0.98, R (PP, Prat) = -0.85 C: R (PratC, MAP) = 0.97, R (PP, Prat) = -0.86 D: R (PratC, MAP) = 0.92, R (PP, Prat) = -0.82 We conclude that Prat carries no substantial incremental value beyond PP, while both Prat and PP are incomplete metrics, requiring simultaneous consideration of MAP. Clinical Relevance- Various ratio-based metrics have been introduced in hemodynamic studies without paying attention to missing components or even redundant candidates. Here we present a uniform method to provide comprehensive insight.

Ventricular and Atrial Ejection Fractions are Associated with Mean Compartmental Cavity Volume in Cardiac Disease

Ejection fraction (EF) is considered to provide clinically useful information. Despite its enormous popularity, with more than 75,000 citations in PubMed, only few studies have traced the origin(s) of its foundation. This fact is surprising, as there are perhaps more papers published that criticize EF, than the number of publications that actually provide a solid (mathematical) basis for its alleged applicability. EF depends on two volume determinations, namely end-systolic volume (ESV) and end-diastolic volume (EDV). EF is defined as 1-ESV/EDV, yielding a metric without physical units. Previously we formulated a robust analytical expression for the nonlinear connection between EF and ESV. Here we extend that approach by providing a formula to illustrate that EF is strongly associated with half the sum (HS) of ESV and EDV. HS is not new, but forms a major component in the recently introduced Global Function Index. For 420 heart failure (HF) patients we found for left ventricular angio data: R(ESV, eDv) = 0.92, R(EF, ESV) = -0.90, and R(EF, HS) = -0.65. For echo (33 HF patients stages A, B, C and D): R(EF, HS) = -0.82. For the right atrium (CMRI in 21 acute myocardial infarction patients): R(EF, HS)=-0.65. For the left atrium (N=86) R (EF, hS)=-0.46. ESV indicates the level to which the ventricle is able to squeeze blood out of the cavity via pressure build-up. In contrast, EF refers to relative volume changes, not to the mechanism of pumping action. We conclude that for each cardiac compartment EF borrows its acclaimed attractiveness from the fact that for a wide patient spectrum the ESVand EDV correlate in a fairly linear manner. Attractiveness of EF features a straightforward mathematical derivation, rather than reflecting underlying physiology. Clinical Relevance - Ejection fraction (EF) is found to reflect (mean) ventricular / atrial size, and is primarily associated with end-systolic volume, which variable in turn highly correlates with diastolic volume. As a mathematical construct, EF has little affinity with "function", which is a central concept in physiology.

Role of Electromechanical Dyssynchrony Assessment During Acute Circulatory Failure and Its Relation to Ventriculo-Arterial Coupling

Introduction

Two parallel paradigms of cardiovascular efficiency and haemodynamic optimisation coexist in haemodynamic research. Targeting ventriculo-arterial (VA) coupling [i.e., the ratio between arterial and ventricular elastance (E_V)] and electromechanical coupling are two promising approaches in acute circulatory failure. However, validation of the parameters of electromechanical coupling in critically ill patients is ongoing. Furthermore, a unifying link between VA and electromechanical coupling may exist, as E_V is correlated with different times of the cardiac cycle.

Materials and Methods

This study was a retrospective analysis of a prospectively collected observational database from one tertiary center ICU. We analyzed the relationship between electromechanical dyssynchrony and acute circulatory failure hemodynamics before and after treatment (i.e., fluid expansion, dobutamine, or norepinephrine infusion). The relationship between electromechanical coupling and VA coupling was also investigated. Adult patients with haemodynamic instability were included. Haemodynamic parameters, including arterial pressure, cardiac index, VA coupling, stroke work index/pressure–volume area (SWI/PVA), t-IVT, and Tei's index, were collected before and after treatment. A t-IVT of >12 s/min was classified as intraventricular dyssynchrony.

Results

We included 54 patients; 39 (72.2%) were classified as having intraventricular dyssynchrony at baseline. These patients with baseline dyssynchrony showed a statistically significant amelioration of t-IVT (from 18 ± 4 s to 14 ± 6 s, p = 0.001), left ventricular E_V [from 1.1 (0.72–1.52) to 1.33 (0.84–1.67) mmHg mL⁻¹, p = 0.001], VA coupling [from 2 (1.67–2.59) to 1.80 (1.40–2.21), p = 0.001], and SWI/PVA [from 0.58 (0.49–0.65) to 0.64 (0.51–0.68), p = 0.007]. Patients without baseline dyssynchrony showed no statistically significant results. The improvement in VA coupling was mediated by an amelioration of E_V. All patients improved their arterial pressure and cardiac index with treatment. The haemodynamic treatment group exhibited no effect on changing t-IVT.

Conclusion

Acute circulatory failure is associated with electromechanical dyssynchrony. Cardiac electromechanical coupling was improved by haemodynamic treatment only if altered at baseline. The improvement of cardiac electromechanical coupling was associated with the improvement of markers of cardiocirculatory efficacy and efficiency (i.e., SWI/PVA and VA coupling). This study was the first to demonstrate a possible link between cardiac electromechanical coupling and VA coupling in patients with acute circulatory failure.