Mayooran Namasivayam

Arterial Stiffness, Its Assessment, Prognostic Value, and Implications for Treatment

Arterial stiffness has been known as a sign of cardiovascular risk since the 19th century. Despite this, accurate measurement and clinical utility have only emerged in recent times. Arterial stiffness and its hemodynamic consequences are now established as predictors of adverse cardiovascular outcome. They are easily and reliably measured using a range of noninvasive techniques, which can be used readily by risk assessment facilities or individual practitioners. The techniques described in this review are based on the pulsatility of the cardiovascular system, utilizing the timing of pulse travel along major arteries and the magnitude of wave reflection. These have enabled better understanding of the ill effects of arterial stiffening, not only on large arteries and the left ventricle, but also on tiny arteries in highly perfused organs such as brain and kidneys. Treatment options, which directly target the consequences of arterial stiffening, as opposed to arbitrary reduction of brachial blood pressure, have proved clinical superiority; optimal therapy entails use of angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, and calcium-channel blockers, as well as vasodilating β-blockers. Arterial stiffness will undoubtedly contribute to cardiovascular assessment and management in future clinical practice. Reviews such as this will hopefully increase awareness of the mounting evidence underlying this transition, and the relevant theory and methodology. As we begin the second decade of the 21st century, we are finally collectively coming to realize what pioneers such as Osler, Roy, Bramwell and Hill foresaw in the 19th and 20th centuries.

Does Wave Reflection Dominate Age-Related Change in Aortic Blood Pressure Across the Human Life Span?

Abstract—Aortic systolic and pulse pressure rise with age because of aortic stiffening. Two factors are responsible: a larger incident wave because of increased aortic characteristic impedance and premature return of wave reflection from peripheral sites. This study aimed to determine the relative contribution of each factor before and after age 60 years. Aortic pressure waveforms were generated for 3682 healthy subjects using a generalized transfer function applied to radial pressure waveforms recorded by applanation tonometry. Linear regression and product of coefficient mediation analysis were performed in the cross-sectional cohort to determine the yearly contribution of the incident and reflected waves (waves measured as first systolic peak and augmented pressure, respectively) to aortic systolic and pulse pressure elevation with age. This was done separately for subjects ≤60 and >60 years of age, with both sexes initially pooled and subsequently separated. Analyses were repeated with correction for height, weight, heart rate, and mean arterial pressure. Before age 60 years, the reflected wave was a greater (P<0.05) contributor to age-related aortic systolic and pulse pressure elevations, with no significant contribution of the incident wave in this age group in sex-pooled analysis. After age 60 years, both incident and reflected waves were significant (P<0.05) and comparable contributors (P difference >0.05) to age-related aortic systolic and pulse pressure elevations. This general pattern was observed in both sexes and persisted after correction for confounders. Wave reflection is important across the life span, whereas aortic characteristic impedance contributes significantly only beyond age 60 years.

Influence of Aortic Pressure Wave Components Determined Noninvasively on Myocardial Oxygen Demand in Men and Women

Myocardial oxygen consumption is increased by arterial stiffening. It is not known precisely how. This study aimed to evaluate the role of the incident and reflected pressure wave in raising myocardial oxygen demand. Central (aortic) pressure waveforms were generated from radial waveforms using a generalized transfer function in 1628 cardiology outpatients (1038 males and 590 females). Aortic waveforms were used to derive measures of incident and reflected waves, as well as to measure mean central systolic pressure (an indicator of systolic ventricular load), left ventricular ejection duration, and tension time index (a surrogate of myocardial oxygen demand) using validated techniques. Incident and reflected waves were measured using the conventional and an alternative method (aortic flow triangulation). Relationships were tested before and after correction for age, height, weight, heart rate, and mean arterial pressure using simple and multivariate linear regression models. Analyses were conducted separately by gender. In both genders (according to conventional or alternative methods of wave measurement), both the incident and reflected wave were strong predictors of tension time index (P<0.001). Both pressure waves raised the mean central systolic pressure (P<0.001). The reflected wave (P<0.001), unlike the incident wave (P>0.05), was also associated with a longer cardiac ejection duration. Tension time index (P<0.0001), mean central systolic pressure (P<0.001), and ejection duration (P<0.0001) were greater in women. Changes in arterial properties alter the nature of pressure wave propagation and predispose to cardiac ischemia (especially in women).

Arterial aging : a review of the pathophysiology and potential for pharmacological intervention

This review begins with a perspective on the effects of arterial aging on society and world events over the past century. Until recently, the use of just one technique to measure blood pressure non-invasively limited progress in understanding the mechanisms involved and the potential of antihypertensive drug therapies. New methods for extracting information from the arterial waveform have followed the (re)introduction of arterial tonometry into clinical practice, together with mathematical analysis in the frequency and time domains. These new methods have exposed the phenomenon of aortic stiffening with age, and early wave reflection arising therefrom, and identified it as the major cause of cardiovascular degeneration. Such findings point to arterial aging as a logical target for the treatment and prevention not only of cardiac, aortic and large artery disease, but also of damage to microvessels in the brain and kidney, which in turn leads insidiously to dementia and renal failure, respectively.

Aortic Augmentation Index and Aging: Mathematical Resolution of a Physiological Dilemma?

To the Editor: Aortic augmentation index (AIx) is frequently used to gauge arterial efficiency through effects of aortic stiffening and peripheral wave reflection.1 It is derived from the aortic pressure waveform and is calculated as aortic augmentation from the initial peak or shoulder to peak pressure divided by pulse pressure. It can be measured directly at cardiac catheterization from waves recorded in the ascending aorta or indirectly and noninvasively from radial artery pressure waves recorded by applanation tonometry at the wrist through use of a generalized transfer function.2 Sometimes the carotid AIx is used as a surrogate of aortic AIx.3 All of the published studies have reported that AIx increases with age. However, this change is not linear, and the curve relating AIx to age flattens beyond age 60 years.4–6⇓⇓ This curvilinear relationship lends itself to various explanations, which stem from the various physiological phenomena that contribute to AIx. From adolescence to middle age, aortic and carotid AIxs rise rapidly with age so that, by extrapolation, a value of 50% might be expected by age 60 years. Clearly, this is impossible, because the reflected wave (the numerator for AIx) cannot exceed amplitude of the incident wave (the major remaining component of the denominator). Another possibility is that, through decreasing myocardial contractility with age, wave reflection has a …

Evaluating the Hemodynamic Basis of Age-Related Central Blood Pressure Change Using Aortic Flow Triangulation

BACKGROUND Pulsatile blood pressure rises with age, especially in the aorta. The comparative role of forward and reflected pressure waves (FW and RW, respectively), determined by aortic flow triangulation has not previously been explored in a large clinical cohort. This study aimed to identify the role of FW and RW in the rise in aortic pulse pressure with age. METHODS For 879 outpatients, aortic pressure waveforms were generated using a validated generalized transfer function applied to radial pressure waves recorded using applanation tonometry. FW and RW were subsequently determined using aortic flow triangulation. Contributions of FW and RW to rise in aortic pulse pressure with age were determined using multivariate linear regression and product of coefficient mediation analysis, with adjustment for height, weight, heart rate, and mean arterial pressure. Comparisons were made by gender and before and after age 60. RESULTS In subjects aged 60 and below, RW was an important contributor to pulsatile pressure elevation with age, but FW was non-contributory in either gender after multivariate correction. In subjects aged above 60, both FW and RW were significant and equal contributors in both genders. CONCLUSIONS In a clinical setting, both FW and RW are important to pulsatile aortic blood pressure across the lifespan, but RW appears to have a more pronounced effect across all ages, whereas FW has less effect in younger persons.

Primary percutaneous coronary intervention for inferior ST‐segment elevation myocardial infarction in a patient supported by the HeartWare left ventricular assist device

A 63‐year‐old man with an ischaemic cardiomyopathy, supported by the HeartWare left ventricular assist device (LVAD), presented with ventricular tachycardia and inferior ST‐elevation myocardial infarction (STEMI) with associated acute right ventricular (RV) dysfunction. He underwent primary percutaneous coronary intervention with balloon angioplasty and placement of three drug‐eluting stents in the proximal‐to‐mid right coronary artery. Post‐procedure, ventricular arrhythmias abated, RV systolic dysfunction resolved and RV size normalised. Percutaneous coronary intervention (PCI) facilitated by the use of miniaturised percutaneous LVAD has become an increasingly available treatment option for high‐risk patients. PCI in patients on established full mechanical circulatory support is not a common occurrence. Indeed, to our knowledge, this is the first case of primary percutaneous coronary intervention on an LVAD‐supported heart reported in the medical literature. The case raises several specific issues that are of peculiar interest to clinicians involved in the care of patients supported by mechanical assist devices who experience an acute coronary syndrome requiring emergent revascularisation.

SAFETY OF MITRAL VALVE REPLACEMENT IN SEVERE SYSTOLIC HEART FAILURE: FIRST INTRA-OPERATIVE EVALUATION OF LEFT VENTRICULAR CONTRACTILE PERFORMANCE DURING OFF-BYPASS, TRANSCATHETER MITRAL VALVE REPLACEMENT

Surgical mitral valve replacement (MVR) in patients with severe systolic heart failure (SHF) may be associated with adverse hemodynamic response due to a sudden rise in ventricular afterload. No study has previously evaluated the intra-operative response of the left ventricle (LV) to MVR without the

Interpreting Blood Pressure in Younger Adults.

The remarkable paper from the Chicago Heart Association Detection Project in Industry Study [(1)][1] studied cardiovascular mortality (3,119 deaths) over 31 years in 27,081 initially well persons, according to initial categorizations of systolic and diastolic hypertension, isolated diastolic

DELINEATING THE MECHANISMS OF AGE RELATED BLOOD PRESSURE CHANGE

methods: For 1474 outpatients, aortic pressure waveforms were generated using a validated generalized transfer function applied to radial pressure waves recorded using applanation tonometry. FW and RW were subsequently determined using aortic flow triangulation, a recent technique supported by aortic MRI. Contributions of FW and RW to rise in aortic systolic and pulse pressure (PPa) with age were determined using univariate and multivariate linear regression and product of coefficient mediation analysis, with adjustment for height, weight, heart rate and mean arterial pressure. Comparisons were made by gender and before and after age 60.