TMAD enters the toolbox for evaluating selected heart transplant patients

Adaptation of the heart is often a blessing for the patient, but sometimes a diagnostic challenge for the responsible physician. The clinical difficulty may be enhanced when employing diagnostic tools that are hard to interpret. Ratio-based metrics are notorious in this respect, and particularly risky in the follow-up evaluation of heart transplant patients. However, measures expressed as physical units contribute to a comprehensive clinical evaluation and guide proper patient management.

Statistics at high-altitudes: Relevance for the interpretation of metrics that reveal cardiac morphology and performance

Survey of four ratio-based metrics, commonly used to evaluate left ventricular performance. The numerator of each ratio is plotted against the corresponding denominator, implying that the slope of the colored line reflects the value of the ratio.9,11 Similar graphs can be constructed for the other cardiac compartments. Data sets obtained at various altitudes and defined with reference to sea level, based on Rao et al.6 Acronyms: E/A unitless ratio of the early (E) and late (A) diastolic wave peak velocities (cm/s); EDD, end-diastolic diameter (mm); EDV, end-diastolic volume (mL); EF, ejection fraction (%); ESD, end-systolic diameter (mm); ESV, end-systolic volume (mL); FS, fractional shortening (%).

Sex differences in diagnostic modalities of atherosclerosis in the macrocirculation

Asymptomatic atherosclerosis begins early in life and may progress in a sex-specific manner to become the major cause of cardiovascular morbidity and death. As diagnostic tools to evaluate atherosclerosis in the macrocirculation, we discuss imaging methods (in terms of computed tomography, positron emission tomography, intravascular ultrasound, magnetic resonance imaging, and optical coherence tomography), along with derived scores (Agatston, Gensini, Leaman, Syntax), and also hemodynamic indices of vascular stiffness (including flow-mediated dilation, shear stress, pulse pressure, augmentation index, arterial distensibility), assessment of plaque properties (composition, erosion, rupture), stenosis measures such as fractional flow reserve. Moreover, biomarkers including matrix metalloproteinases, vascular endothelial growth factors and miRNAs, as well as the impact of machine learning support, are described. Special attention is given to age-related aspects and sex-specific characteristics, along with clinical implications. Knowledge gaps are identified and directions for future research formulated.

Sex differences in diagnostic modalities of coronary artery disease: Evidence from coronary microcirculation

Although atherosclerosis is usually considered a disease of the large arteries, risk factors for atherosclerosis also trigger structural and functional abnormalities at a microvascular level. In cardiac disease, microvascular dysfunction is especially relevant in women, among whom the manifestation of ischemic disease due to impaired coronary microcirculation is more common than in men. This sex-specific clinical phenotype has important clinical implications and, given the higher pre-test probability of coronary microvascular dysfunction in females, different diagnostic modalities should be used in women compared to men. In this review, we summarize invasive and non-invasive diagnostic modalities to assess coronary microvascular function, ranging from catheter-based evaluation of endothelial function to Doppler echocardiography and positron emission tomography. Moreover, we discuss different clinical settings in which microvascular disease plays an important role, underlining the importance of choosing the right diagnostic modality depending on the sex of the patients.

Sex-specific Evaluation of Ventricular Ejection Fraction and End-Systolic Volume Applied to Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) can decrease the risk of heart failure (HF) events in relatively asymptomatic patients with a reduced ejection fraction (EF) and wide QRS complex. However, individual response to this type of therapy varies widely. Often based on either EF increase or end-systolic volume (ESV) decrease as criterion, a subgroup of super-responders has been described. Therefore, it is important to determine factors that can predict a favorable response and identify those patients who may benefit from CRT. With this goal in mind we explored the possible role of ESV.To improve insight in ventricular pump function we previously introduced the volume regulation graph (VRG), relating ESV to end-diastolic volume (EDV). An individual patient is uniquely defined by the prevailing working point in the volume domain. The traditional metric EF can be graphically derived for each working point. The nonlinear association between EF and ESV is given by EF = 1 + γ {ESV / (δ - ESV)}, with empirical constants γ and δ. The impact of CRT super-responders on EF can be evaluated, taking into account sex-specific ESV values. Based on available regression equations we modeled the impact on EF (as percent points) resulting from CRT-induced fractional ESV changes expressed as % of baseline ESV. Our analysis confirms clinical findings, indicating that CRT super-responders are likely to be women, and clarify why a specific reduction of ESV cannot be directly translated into EF improvement. We propose that the EF as CRT criterion should be abandoned and replaced by sex-specific ESV evaluations.Clinical Relevance- Response to CRT should be evaluated in a sex-specific manner. The smaller heart size in women has implications for the interpretation of percentwise reductions of ESV and their translation into an associated increase of EF.

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.

Ventricular Ejection Fraction and Global Strains in Connection with the Volume Regulation Graph

Ejection fraction (EF) is traditionally considered useful to infer ventricular function. Newer metrics such as global function index (GFI) and various strains add supplemental diagnostic or prognostic value. All these candidates refer to dimensionless ratios, rather than to the characteristics of the underlying components. Therefore, we introduced the volume regulation graph (VRG), relating end-systolic volume (ESV) to end-diastolic volume (EDV). An individual patient is then uniquely defined by the prevailing working point in the volume domain. Alternatively, the combination of EF=(1-ESV/EDV) and any suitable companion (denoted as C) metric (e.g. the Pythagorean mean) specifies this working point.An expression relates EF to global longitudinal (GLS) and circumferential strain (GCS): ESV/EDV = (GLS+1) (GCS+1)2, resembling the empirical regression equation for the VRG. However, the latter has a non-zero intercept (mL). The discrepancy can be solved by the introduction of one or more pertinent companion metrics.We studied 96 patients by cardiac magnetic resonance imaging and calculated EF, EFC, GFI, GLS and GCS. The GFI is inversely related to GLS (R2=0.26). For regression we found: ESV=0.74 EDV-27.0 with R2=0.81 for N=96. Similar results were obtained for echocardiography data (N=25). Graphs relating EF to GLS and GCS indicate that EFC can distinguish patients with nearly identical values for these 3 metrics.Thus, the VRG offers a unifying framework that visualizes the association between ESV and EDV, while documenting iso-EF and iso-EFC trajectories. Newer metrics including GFI, GLS and GCS require consideration of a companion variable such as EFC to permit a comprehensive analysis.Clinical Relevance- The VRG allows insight into ventricular functioning and illustrates the working point concept. Companion metrics (having a physical dimension) should be considered in conjunction with any traditional ratio-based index.

Coronary Flow Velocity Reserve by Echocardiography: Beyond Atherosclerotic Disease

Coronary flow velocity reserve (CFVR) is defined as the ratio between coronary flow velocity during maximal hyperemia and coronary flow at rest. Gold-standard techniques to measure CFVR are either invasive or require radiation and are therefore inappropriate for large-scale adoption. More than 30 years ago, echocardiography was demonstrated to be a reliable tool to assess CFVR, and its field of application rapidly expanded. Although initially validated to assess the hemodynamic relevance of a coronary stenosis, CFVR by echocardiography was later used to investigate coronary microcirculation. Microvascular dysfunction was detected in many different conditions, ranging from organ transplantation to inflammatory disorders and from metabolic diseases to cardiomyopathies. Moreover, it has been proven that CFVR by echocardiography not only detects coronary microvascular involvement but is also an effective prognostic factor that allows a precise risk stratification of the patients. In this review, we will summarize the many applications of CFVR by echocardiography, focusing on the coronary involvement of systemic diseases.

Case report on right ventricular mural endocarditis, not diagnosed clinically, but histopathologically after cardiac surgery

Background

Right ventricular mural endocarditis (RVME) is an extremely rare type of infective endocarditis that can occur even in the absence of predisposing factors. The diagnosis is a challenge when no causative pathogen can be detected.

Case summary

A previously healthy young man was admitted to a local hospital with a diagnosis of prolonged febrile syndrome and treated for acute sinusitis. As complaints returned, he was hospitalized 3 weeks later, where an echocardiogram demonstrated multiple mobile masses in the right ventricle, and a computed tomography scan revealed extensive pulmonary thromboembolism. During surgery, the endocardial masses were excised, and the pathologist considered an inflammatory myofibroblastic tumour. Despite appropriate medication and initial improvements, the complaints persisted, and 2 weeks after the surgery, the patient returned to the hospital. Imaging studies documented reappearance to the previous findings, whereas blood cultures remained negative. During the second surgery, the new masses resembling vegetations were excised, and histologic analysis indicated infective endocarditis. Adjusted medication was given for 30 days. Just before discharge, no vegetations were seen. At follow-up, 5 years later, he was in a healthy condition.

Discussion

Despite careful examinations, initial treatments according to standard protocols were unsuccessful. At final discharge, the patient reported that a tattoo complication prior to the first hospitalization was treated by antibiotics but that he did not complete the course. This omission in the communication further complicated the diagnostic and management processes, leading to surgical interventions that could have been prevented if the neglected antibiotic course was properly disclosed.

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.

Various Approaches to Define the Volume Intercept of the Ventricular End-Systolic Pressure-Volume Relationship: Implications for Statistical Analysis

Ventricular pump function is often characterized by the (non)linear end-systolic pressure-volume relationship (ESPVR). For each working point on that curve the tangent along with the intercept (Vo) reflect contractile state. Vo on the abscissa is an extrapolated point without physiological meaning, and may be negative. To obtain positive values for the intercept, investigators often choose a non-zero pressure level. Although this preference is mathematically sound, we demonstrate that statistical evaluations may yield different results, depending on the pressure level selected. Published data on 17 cardiac patients representing three diagnostic groups were analyzed, showing dicrotic notch pressure based values -14<Vo<119 mL/m²• At 20, 40, 60, 80 and 100 mmHg levels all intercepts were positive, but statistical outcomes varied when comparing the 3 groups, depending on the pressure level selected, e.g. ranging from P=0.03 to 0.28. Also, we found that the correlation between intercept value Vo and end-systolic volume varies with the choice made for the pressure level. However, as there is no need to explore alternatives for the intercept, we conclude that the traditional route for the estimation of Vo (i.e. extrapolated to zero pressure) is to be preferred and this practice warrants adequate comparison of outcomes generated by all studies. Clinical Relevance- Personal preference for an alternative intercept definition for the ESPVR does not serve any relevant goal but rather implies that the statistical outcomes are altered thus hampering interpretation of data when comparing patient groups or assessing the effect of clinical intervention.

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.

Coronary Flow Evaluation in Heart Transplant Patients Compared to Healthy Controls Documents the Superiority of Coronary Flow Velocity Reserve Companion as Diagnostic and Prognostic Tool

Background

Distinct contributions by functional or structural alterations of coronary microcirculation in heart transplantation (HT) and their prognostic role have not been fully elucidated. We aimed to identify the mechanisms of coronary microvascular dysfunction (CMD) in HT and their prognostic implications.

Methods

134 patients, surviving at least 5 years after HT, without evidence of angiographic vasculopathy or symptoms/signs of rejection were included. 50 healthy volunteers served as controls. All underwent the assessment of rest and hyperemic coronary diastolic peak flow velocity (DPVr and DPVh) and coronary flow velocity reserve (CFVR) and its inherent companion that is based on the adjusted quadratic mean: CCFVR = √{(DPVr)2 + (DPVh)2}. Additionally, basal and hyperemic coronary microvascular resistance (BMR and HMR) were estimated.

Results

Based on CFVR and DPVh, HT patients can be assigned to four endotypes: endotype 1, discordant with preserved CFVR (3.1 ± 0.4); endotype 2, concordant with preserved CFVR (3.4 ± 0.5); endotype 3, concordant with impaired CFVR (1.8 ± 0.3) and endotype 4, discordant with impaired CFVR (2.0 ± 0.2). Intriguingly, endotype 1 showed lower DPVr (p &lt; 0.0001) and lower DPVh (p &lt; 0.0001) than controls with lower CFVR (p &lt; 0.0001) and lower CCFVR (p &lt; 0.0001) than controls. Moreover, both BMR and HMR were higher in endotype 1 than in controls (p = 0.001 and p &lt; 0.0001, respectively), suggesting structural microvascular remodeling. Conversely, endotype 2 was comparable to controls. A 13/32 (41%) patients in endotype 1 died in a follow up of 28 years and mortality rate was comparable to endotype 3 (14/31, 45%). However, CCFVR was &lt; 80 cm/s in all 13 deaths of endotype 1 (characterized by preserved CFVR). At multivariable analysis, CMD, DPVh &lt; 75 cm/s and CCFVR &lt; 80 cm/s were independent predictors of mortality. The inclusion of CCFVR &lt; 80 cm/s to models with clinical indicators of mortality better predicted survival, compared to only adding CMD or DPVh &lt; 75 cm/s (p &lt; 0.0001 and p = 0.03, respectively).

Conclusion

A normal CFVR could hide detection of microvasculopathy with high flow resistance and low flow velocities at rest. This microvasculopathy seems to be secondary to factors unrelated to HT (less rejections and more often diabetes). The combined use of CFVR and CCFVR provides more complete clinical and prognostic information on coronary microvasculopathy in HT.

Multiparametric analysis of coronary flow in psoriasis using a coronary flow reserve companion

BACKGROUND

Coronary microvascular dysfunction (CMD) is usually evaluated measuring coronary flow velocity reserve (CFVR). A more comprehensive analysis of CFVR including additional consideration of the associated logical companion-CFVR, where hyperemic diastolic coronary flow velocity may act as surrogate, was applied in this study to elucidate the mechanism of CMD in psoriasis.

METHODS AND RESULTS

Coronary flow velocity reserve was analysed using transthoracic echocardiographs of 127 psoriasis patients (age 36 ± 8 years; 104 males) and of 52 sex- and age-matched healthy controls. CFVR determination was repeated in the patient subgroup (n = 78) receiving anti-inflammatory therapy. Baseline and hyperemic microvascular resistance (MR) were calculated. CMD was defined as CFVR ≤ 2.5. Four endotypes of CMD were identified referring to concordant or discordant impairments of hyperemic flow or CFVR. We evaluated the companion-CFVR, as derived from the quadratic mean of hyperemic and diastolic flow velocity at rest. Coronary flow parameters, including CFVR (p = 0.01), were different among the two endotypes having CFVR > 2.5. Specifically, all 11 (14%) patients with CFVR deterioration despite therapy, belonged to endotype 1, and had higher baseline and hyperemic MR (p < 0.0001, both). Interestingly, while CFVR was comparable in patients with worsened versus those with improved CFVR, the companion-CFVR could discriminate by being lower in patients with worsened CFVR (p = 0.01).

CONCLUSIONS

The reduced CFVR in psoriasis is driven by decreased companion-CFVR, combined with increased hyperemic MR. Adoption of the mandatory companion-CFVR enables a personalized characterization superior to that achieved by exclusive consideration of CFVR.

Left Ventricular Global Function Index and the Impact of its Companion Metric

Left ventricular (LV) global function index (LVGFI) has been introduced as a volume-based composite metric for evaluation of ventricular function. The definition formula combines stroke volume (SV), end-systolic volume (ESV), end-diastolic volume (EDV) and LV mass/density. Being a dimensionless ratio, this new metric has serious limitations which require evaluation at a mathematical and clinical level. Using CMRI in 96 patients we studied LV volumes, various derived metrics and global longitudinal strain (GLS) in order to further characterize LVGFI in three diagnostic groups: acute myocarditis, takotsubo cardiomyopathy and acute myocardial infarction. We also considered the LVGFI companion (C), derived from the quadratic mean. Additional metrics such as ejection fraction (EF), myocardial contraction fraction (MCF) and ventriculo-arterial coupling (VAC), along with their companions (MCFC and VACC) were calculated. All companion metrics (EFC, LVGFIC, MCFC, and VACC) showed sex-specific differences, not clearly reflected by the corresponding ratio-based metrics. LVGFI is mathematically coupled to both EF (with R = 0.86) and VAC (R = 0.87), which observation clarifies why these metrics not only share similar prognostic values but also identical shortcomings. We found that the newly introduced LVGFIC has incremental value compared to the single use of LVGFI, EF, or GLS, when characterizing the three patient groups.

Case report on the importance of longitudinal analysis of left ventricular end-systolic volume, rather than ejection fraction, in a heart transplant patient

Background

Sequential determinations of left ventricular (LV) volume constitute a cornerstone in the mechanical performance evaluation of any heart transplant (HTX) patient. A comprehensive analysis of volumetric data offers unique insight into adaptation and pathophysiology.

Case summary

With a focus on eight sequential biplane angiocardiographic LV end-systolic volume (ESV) determinations, we evaluate the clinical course of a male patient following HTX (female donor) at the age of 61 years. This former smoker had a history of chronic obstructive pulmonary disease, hypertension, and hypercholesterolaemia refractory to treatment, and presented with multivessel coronary artery disease. The later course was complicated by pulmonary hypertension, an abdominal aortic aneurysm, and secondary chronic kidney disease. After an additional episode of pulmonary embolism, the patient died at the age of 79. At one point, the ESV was > 700% higher than the starting value, and actually by far exceeded the relative change of any other volume-based metric evaluated, including ejection fraction (EF).

Discussion

The longitudinal study of LV volumetric data in HTX patients offers a unique window to the pathophysiology of remodelling and sex-specific adaptation processes. The present case documents that proper analysis of serial findings form a rich source of clinically relevant information regarding disease progression. End-systolic volume is the primary indicator, in contrast to the popular metric EF. This finding is supported by population-based studies reported in the literature. We conclude that comprehensive analysis of volumetric data, particularly ESV, contributes to personalized medicine and enhances insight into LV (reverse) remodelling, while also informing about prognosis.

Sex-Specific Interpretation of Coronary Flow Reserve and Fractional Flow Reserve Metrics, Including Their Companions

BACKGROUND

Impairment of coronary flow is usually evaluated by considering the ratio of two measurements. Fractional flow reserve (FFR) estimates impact on an epicardial artery by taking mean post-stenotic pressure divided by mean aortic pressure, both obtained during adenosine induced hyperemia. Coronary flow reserve (CFR) compares hyperemic flow or velocity with the baseline situation, also as a ratio. As severity of underlying pathology may differ for men and women, we investigate the impact of these differences on relevant metrics.

METHODS

As sex associated differences may cancel out in a ratio, this weakness of a ratio can be compensated by analyzing the intrinsic companion (C) and consider polar coordinates. Thus, besides the familiar ratio based metrics, we also analyze FFRC and CFRC. Outcomes of in silico studies are employed to extrapolate actual patient data and predict consequences. For FFR 129 patients (38 women) were invasively studied using pressure wires. CFR was measured noninvasively for the left anterior descending coronary artery by recording ultrasound based Doppler velocity in 114 individuals (28 women).

RESULTS

The FFR can be identified as an indicator of the pressure gradient over the stenosis (R=-0.90), while FFRC differs for men compared to women (P=0.04) and correlates (R=0.93) with post-stenotic driving pressure. CFR shows a difference for men versus women (P=0.04) and is best associated with hyperemic flow (R=0.64), whereas CFRC relates to hyperemia recruited velocity (R=0.97). Simulation studies show that FFR may differ for both sexes when considering elderly.

CONCLUSIONS

Analysis of ratios require inclusion of the companion, and sex-specific differences deserve attention.

Ratiology and a Complementary Class of Metrics for Cardiovascular Investigations

Cardiovascular investigations often involve ratio-based metrics or differences: ejection fraction, arterial pressure augmentation index, coronary fractional flow reserve, pulse pressure. Focusing on a single number (ratio or difference) implies that information is lost. The lost companions constitute a well-defined but thus far unrecognized class, having additive value, a physical dimension, and often a physiological meaning. Physiologists should play a prominent role in exploring these complementary avenues and also define alternatives.

Polar Coordinate Description of Blood Pressure Measurements and Implications for Sex-Specific and Personalized Analysis

Vascular properties and their associated impact on cardiovascular risk factors are often evaluated by metrics such as pulse pressure (PP) and the augmentation index (AIx). All derived metrics are essentially based on the combination of blood pressure recordings. These clinically used metrics typically concern a difference (as in PP) or a ratio (as in AIx). A polar coordinate description reveals the companion (C) of the traditional metric. The aim of this study is to evaluate the impact of PPC and AIxC by analyzing both patient data and a detailed data set on healthy children derived from the literature.Companions are calculated using the Pythagorean theorem, and show that PPC is related to mean arterial pressure, thus complementing the biomarker PP. Also, inflection pressure is tied to systolic pressure, implying a possible simplification of obtaining the numerical value of AIx. Outcomes for adults and children are comparable. We conclude that derived metrics such as PP and AIx are incomplete. The associated companion metrics PPC and AIxC can easily be calculated. They add clinically relevant information without the need to perform additional measurements. Combination of traditional and the newly described companion metrics permits more precise characterization of individual patients.

Fractional Flow Reserve Evaluated as Metric of Coronary Stenosis - A Mathematical Model Study

Introduction: Coronary arterial stenosis may impair myocardial perfusion with myocardial ischemia and associated morbidity and mortality as result. The myocardial fractional flow reserve (FFR) is clinically used as a stenosis-specific index. Aim: This study aims to identify the relation between the FFR and the degree of coronary arterial stenosis using a simple mathematical model of the coronary circulation. Methods: A mathematical model of the coronary circulation, including an arterial stenosis of variable degree, was developed. The relation between the FFR and the degree of stenosis (defined as the fractional cross sectional area narrowing) was investigated, including the influence of the aortic and venous pressures and the capillary resistance. An additional study concerning 22 patients with coronary artery disease permits comparison of clinical data and in silico findings. Results: The FFR shows an S-shaped relationship with the stenosis index. We found a marked influence of venous and aortic pressure and capillary resistance. The FFR is accompanied by a clinically relevant co-metric (FFR C ), defined by the Pythagorean sum of the two pressures in the definition formula for FFR. In the patient group the FFR C is strongly related to the post-stenotic pressure (R = 0.91). The FFR C requires establishment of a validated cut-off point using future trials. Conclusion: The S-shaped dependence of FFR on the severity of the stenosis makes the FFR a measure of the ordinal scale. The marked influences of the aortic and venous pressures and the capillary resistance on the FFR will be interpreted as significant variations in intra- and inter-individual clinical findings. These fluctuations are partly connected to the neglect of considering the FFR C . At otherwise identical conditions the FFR as measured at baseline differs from the value obtained during hyperemic conditions. This expected observation requires further investigation, as the current hyperemia based evaluation fails to take advantage of available baseline data.

Heart Failure Phenotypes Require Sex-Specific Criteria Which Are Based on Ventricular Dimensions

Ejection fraction (EF) is often used as a criterion to establish diagnostic phenotypes of heart failure (HF). Because EF is a derived metric based on end-systolic volume (ESV) and end-diastolic volume (EDV), it is more logical to consider ESV or EDV as cut-off marker. We concentrate on the impact of ESV, which has the advantage of being linearly related to EDV and nonlinearly with EF, both with highly significant correlations. In particular we also analyze if HF classification should distinguish between females and males.ESV and EDV were determined by biplane angiography in 197 HF patients (67 women). As body surface indexed (i) ESVi values for adult healthy females are smaller than for males, we employ classes of ESVi (bins of 10 mL/m²) to group preserved and reduced EF's (cut-off at 50%) for HF. Reference values regarding mean and standard deviation for ESVi are based on a control group (N=155, 65 women) without HF. For interpretation of the findings we use the documented universal relationship connecting EF to ESV: EF = 1 + c₁ {ESV / (c₂ - ESV)}, where c₁ and c₂ are population-based sex-independent constants. In the reference group ESVi (mL/m²) in women (27.4 ± 27.6) is smaller (P=0.0026) than in their male counterparts (43.6 ± 37.5). Similarly, for HF the ESVi in women (45.7 ± 41.4) is smaller (P=0.0033) than in men (64.2 ± 41.4). This signifies (see formula above) that women have higher values for EF, primarily resulting from smaller ventricular size related to their sex, and not exclusively reflecting disease state. Current phenotype classification based on pooled data for males and females may be inappropriate for either sex.The significantly smaller ESVi observed in women has direct consequences for the traditional classification based on EF cutoff values for HF. Sex-specific criteria (regarding ESVi or EF) for HF phenotypes are warranted, and expectedly have substantial consequences for identification, classification, and management of HF patients.

Left ventricular volume analysis as a basic tool to describe cardiac function

The heart is often regarded as a compression pump. Therefore, determination of pressure and volume is essential for cardiac function analysis. Traditionally, ventricular performance was described in terms of the Starling curve, i.e., output related to input. This view is based on two variables (namely, stroke volume and end-diastolic volume), often studied in the isolated (i.e., denervated) heart, and has dominated the interpretation of cardiac mechanics over the last century. The ratio of the prevailing coordinates within that paradigm is termed ejection fraction (EF), which is the popular metric routinely used in the clinic. Here we present an insightful alternative approach while describing volume regulation by relating end-systolic volume (ESV) to end-diastolic volume. This route obviates the undesired use of metrics derived from differences or ratios, as employed in previous models. We illustrate basic principles concerning ventricular volume regulation by data obtained from intact animal experiments and collected in healthy humans. Special attention is given to sex-specific differences. The method can be applied to the dynamics of a single heart and to an ensemble of individuals. Group analysis allows for stratification regarding sex, age, medication, and additional clinically relevant covariates. A straightforward procedure derives the relationship between EF and ESV and describes myocardial oxygen consumption in terms of ESV. This representation enhances insight and reduces the impact of the metric EF, in favor of the end-systolic elastance concept advanced 4 decades ago.

Heart Transplantation Survival and Sex-Related Differences

Orthotopic heart transplantation (OHT) is the "gold standard" treatment for patients with end-stage heart failure, with approximately 5000 transplants performed each year worldwide. Heart transplantation survival rates have progressively improved at all time points, despite an increase in donor and recipient age and comorbidity and greater recipient urgency; according to the registry of the International Society of Heart and Lung Transplantation (ISHLT), the median survival of patients posttransplantation is currently 12.2 years.Long-term survival is sub-optimal, and outcomes after OHT remain constrained by the development of acute rejection and cardiac allograft vasculopathy (CAV). Moreover, donor organs are in short supply, making optimal organ utilization an ongoing priority. For these reasons, substantial interest continues to exist in identifying factors portending increased survival and improved organ utilization.

Women and Men in the History of Western Cardiology: Some Notes on Their Position as Patients, Role as Investigational Study Subjects, and Impact as Professionals

Nowadays, it is generally appreciated that studies in the medical field should not only include sex-related aspects but also consider age. In the past, taking the era of Hippocrates as a starting point for the Western medical sciences, such aspects were less urgent and barely relevant. However, considering such details during daily life became increasingly important as the traditional roles of men and women in society and household converged. In the Western world, this fundamental transition process started recently and is advancing at an accelerated pace. Research about the role of women has also evolved, starting from plain history about the lives of women to a description of the relation between men and women, resulting in the gender concept. The present survey highlights a historical selection of observations referring to the impact of men and women on the medical sciences, as patient, study object, and professional. Whenever relevant, focus will be on the field of cardiovascular investigations as documented in the Western world. Rather than being exhaustive, we focus on a few remarkable icons, including Trota of Salerno, Hildegard von Bingen, and Miguel Serveto.

Cardiophysiology Illustrated by Comparing Ventricular Volumes in Healthy Adult Males and Females

Recent advances in cardiac imaging techniques have substantially contributed to a growing interest in the analysis of global cardiac chamber dimensions and regional myocardial deformation. During the cardiac cycle, ventricular luminal volume varies due to the contraction process, which also confers a shape change including substantial alteration of long axis length, as well as rotation of the base compared to the apex. Local deformation can be assessed by strain (rate) analysis. Reviewing the present literature, it must be concluded that there is no single metric available to comprehensively characterize ventricular function. Every candidate advanced thus far has been found to incompletely reflect ventricular performance. This observation is not surprising in view of the complexity of the cardiac pump system. Additionally, sex-specific modifiers may play a role. More than three decades ago, it was shown that on average the ventricular volume is smaller in healthy women compared to matched males. Therefore, the present contribution concerns the interpretation of data derived from the healthy heart in both men and women. Starting from the classical Starling concept, we apply a simple mathematical transformation which permits an insightful representation of ventricular mechanics. Relating end-systolic volume (ESV) to end-diastolic volume creates the ventricular volume regulation graph which features the pertinent working point of an individual heart. This fundamental approach illustrates why certain proposed performance indexes cannot individually reveal the essence of ventricular systolic function. We demonstrate that particular metrics are highly interconnected and just tell us the same story in a different disguise. It is imperative to understand which associations exist and if they expectedly are (nearly) linear or frankly nonlinear. Notably, ejection fraction (EF) is primarily determined by ESV, while in turn EF is not much different from ventriculo-arterial coupling (VAC). Insight into cardiac function is promoted by identification of the paramount/essential components involved. The smaller ESV (p < 0.0001) implies that EF is higher in women and may also have consequences for VAC.

Cardiovascular Implications of Diabetes, Metabolic Syndrome, Thyroid Disease, and Cardio-Oncology in Women

Cardiovascular disease may be associated with several comorbidities, including diabetes mellitus, thyroid disorders, and the metabolic syndrome, which are predominantly observed in women and often starting at particular ages. In addition, common treatment options for carcinomas frequently seen in women may induce serious cardiotoxic effects. We review the scope of the problem, the pathophysiologic mechanisms involved, as well as the resulting abnormalities regarding cardiac structure and function as observed by using imaging techniques.

Arterial Flow, Pulse Pressure and Pulse Wave Velocity in Men and Women at Various Ages

The increase in pulse pressure (PP) that occurs with advancing age is predominantly due to reduced arterial distensibility leading to decreased aortic compliance, particularly in the elderly, in whom high blood pressure mainly manifests as isolated systolic hypertension. Since age-related changes in stroke volume are minimal compared with changes in PP, PP is often considered a surrogate measure of arterial stiffness. However, since PP is determined by both cardiac and arterial function, a more precise and reliable means of assessment of arterial stiffness is arterial pulse wave velocity (PWV), a parameter that is only dependent on arterial properties. Arterial stiffness as measured by PWV has been found to be a powerful pressure-related indicator for cardiovascular morbidity and mortality. We analyzed PP and PWV in men and women of various age groups in healthy volunteers as well as cardiac patients with different types of diseases. The findings identified several striking sex-specific differences which demand consideration in guidelines for diagnostic procedures, for epidemiological analysis, and in evaluation of therapeutic interventions.

Sex-specific aspects of left and right ventricular volume regulation in patients following tetralogy of Fallot repair

Ejection fraction (EF) is applied as a clinically relevant metric to assess both left (LV) and right ventricular (RV) function. EF depends on the interplay between end-systolic volume (ESV) and end-diastolic volume (EDV). The role of the two constitutive components is of particular interest for the follow-up study of Fallot patients at risk for RV volume overload. The volume regulation graph (VRG) relates ESV to EDV and has been advanced as a central tool to describe LV and RV function. The method permits additional analysis of the impact of clinically relevant determinants such as sex and age. Following Fallot repair and using MRI we evaluated LV and RV volumes in 124 patients (50 females), who were not taking any medication. Volumes were indexed for body surface area (BSA). The VRG regression lines are similar for both sexes, also when stratified for age (i.e. younger or older than 18 years), and different for LV and RV. However, RV ESV is larger (P=0.039) for adult males, as is RV EDV (P=0.026) in boys, relative to their female counterparts. For LV ESV we also found larger volumes, but only in boys (P=0.023) compared to girls. Average EF (only for RV) is lower in adult men compared to women (P=0.012), and to boys (P=0.007). These findings are partly in contrast with common observations made in individuals without a history of cardiac disease, where (with BSA indexation) LV and RV volumes are similar in children, but consistently larger in adult males. These results highlight the age- and sex-specific volumetric aspects of remodeling following surgery in Fallot patients, and emphasize the pivotal role of ESV size in both RV and LV.

Monte Carlo method applied to the evaluation of the relationship between ejection fraction and its constituent components

Ventricular function is routinely assessed by applying the clinically accepted metric ejection fraction (EF). The numerical value of EF depends on the interplay between end-systolic volume (ESV) and end-diastolic volume (EDV). The relative impact of the two constitutive components has received little attention. Pediatric cardiologists are interested in EF vs ESV when evaluating various congenital abnormalities. Following successful surgical intervention of Fallot tetralogy, many of these patients receive follow-up, not only during childhood, but also when being adults. Cardiologists diagnosing and treating elderly patients often analyze EF vs EDV, notably for phenotyping heart failure patients. Therefore, we study EF vs ESV as well as EF vs EDV in more detail. We explore the fundamentals of EF while analyzing a Fallot patient group. Three routes were followed, namely nonlinear regression, by implementing a Monte Carlo approach to generate EDV on the basis of known ESV values, and by using a theoretical graphical derivation. Our MRI-based post Fallot repair study includes left (LV) and right ventricular (RV) data (N=124). Using a robust approach we employed nonlinear regression with ESV as an independent variable. EDV was also assessed by Monte Carlo generated values for stroke volume within a physiological range. In all cases ESV emerges as the dominant component of EF, with less (P<;0.0001) impact of EDV. Using three independent routes we demonstrate that values for EF primarily depend on the corresponding ESV. This relationship is nonlinear, and correlation is always better with ESV compared to EDV in these patients, and confirmed in random number modeling studies.

Effective arterial elastance and arterial compliance in heart failure patients with preserved ejection fraction

Heart failure (HF) patients have often been observed to have their ejection fractions somewhat preserved (HFpEF). Since left ventricular (LV) ejection is dependent on the coupled arterial load, the preserved ejection may be dependent on the effective arterial elastance (Ea). Whether this is indeed the case is subject to further analysis. We investigated this aspect in 67 patients with cardiac disease; 34 of them met the matching criteria for HFpEF. Both Ea, an arterial system (ASy) property, and aortic compliance (C), a physical property, were obtained in an attempt to differentiate the LV-ASy interaction in HFpEF and HFrEF (reduced ejection fraction) patients. Outcome of the study allowed us to conclude that Ea does not parallel changes in C. While Ea may be useful in assessing the severity of HFrEF, it is a weak indicator of EF dependence in HFpEF patients.

Left ventricular volume regulation in heart failure with preserved ejection fraction

Ejection Fraction (EF) has attained the recognition as indicator of global ventricular performance. Remarkably, precise historical origins promoting the apparent importance of EF are scant. During early utilization EF has been declared a gold standard for the evaluation of the heart as a pump. In contrast, during the last two decades, clinicians have developed a measure of doubt in the universal applicability of EF. This reluctance lead to the introduction of a new and prevalent syndrome in which heart failure (HF) is diagnosed as having a preserved EF (pEF). We examine the existing criticism regarding EF, and describe a novel avenue to characterize ventricular function within the unifying framework of cardiac input–output volume regulation. This approach relates end-systolic volume (ESV) to end-diastolic volume (EDV), and derives for a subgroup matching pEF criteria a distinct pattern in the ESV–EDV domain. In patients with pEF (n = 34), a clear difference (P < 0.0004) in the slope of the regression line for ESV versus EDV was demonstrated compared to control patients with EF < 50% (n = 29). These findings are confirmed by analysis of data presented in two independent publications. The volume regulation approach proposed employs primary end-point determinants (such as ESV and EDV) rather than derived quantities (e.g., the ratio EF or its differential parameter, that is, stroke volume) and confirms a distinct advantage over the classical Starling curve. Application of the ESV-EDV-construct provides the basis and clarifies why some patients present as HFpEF, while others have reduced EF.

Hemodynamic interventions and the pressure-diameter loop of the left ventricle and the proximal aorta in the conscious dog

The dynamics of the left ventricle (LV) have been extensively investigated. However, most studies refer to steady state conditions. We addressed the beat-to-beat variations resulting from hemodynamic interventions analyzed in the chronically instrumented dog. This approach permits serial studies in the same subject under physiological conditions. In particular we investigated the end-systolic pressure-dimension relationship and characteristics of the proximal aorta. The findings obtained during basal conditions, exercise and pharmacologic intervention indicate that several universal regulatory mechanisms are involved, besides various phenomena that exhibit a substantial degree of variability.

On the optimal defibrillation waveform--how to reconcile theory and experiment?

Medical intervention by electrical current as applied to humans or animals may have tremendous therapeutic impact if delivered while being carefully controlled. Otherwise, the situation can be harmful in terms of injury or even become lethal. These consequences demand close inspection of all relevant biological and technical factors. Regarding methods to counter fibrillation of the heart substantial progress has been made, but defining a gold standard for the waveshape and energy delivery remains a serious challenge. The anticipated answer is not simply a range somewhere between a maximum and a minimum, but most likely an "intelligently" selected case-specific optimum, delicately positioned between effective and unsafe. Combining insight from theory with pertinent experimental findings may offer a clearer view on an unresolved issue that often points to a cross-road of life and death.

Quantifying ventricular fibrillation: in silico research and clinical implications

Cardiovascular disease remains the leading cause of death in otherwise healthy humans. In particular, most cases of sudden cardiac death occur as a result of failure of the mechanical function of the heart which is triggered by a turbulent pattern of electrical excitation of the heart e.g., ventricular fibrillation (VF). Although the exact mechanisms of VF remain unknown, increasing evidence indicates that it is organized by multiple reentrant sources (wavelets).