Diastolic dysfunction of the left ventricle. A review of the physiology, causes, diagnosis, treatment and implications

Diastolic dysfunction of the left ventricle frequently occurs in people with left ventricular hypertrophy and coronary artery disease. It is a common cause of congestive heart failure, especially in the elderly. The mechanism of diastolic dysfunction, its causes, diagnosis and treatment, are reviewed. These are important factors to a Medical Director who must assess the results of non-invasive studies. Alerted by the possibility of diastolic dysfunction, the Medical Director can be more sensitive to other signs and symptoms that may represent early signs of congestive heart failure or ischemia.     

Matters of the athletic heart

Frequently an underwriter or medical director will question whether an increase in left ventricular mass represents pathologic left ventricular hypertrophy (LVH) or physiologic changes related to exercise. The LVH condition reflects end-organ damage related to abnormal hemodynamic stresses and confers an increased morbidity and mortality risk. When left ventricular mass is increased because of exercise, measured changes represent a normal, healthy cardiovascular system responding to the demands of that exercise. This article summarizes medical findings that distinguish pathologic LVH from an "athletic heart."     

Utilizing NT-proBNP in the selection of risks for life insurance

Brain natriuretic peptide (BNP) is a counter-regulatory hormone produced mainly by ventricular myocardium. Early research studies were performed to ascertain its value in the diagnosis of congestive heart failure in acute care settings. Subsequent studies have explored its utility in screening for asymptomatic left ventricular dysfunction in the community, determining prognosis in coronary artery disease, appropriate timing of surgery in valve disorders, and in evaluating many other cardiac diseases. This review summarizes the current status of medical literature, introduces a new test to the insurance industry.     

Nonsustained wide QRS tachycardia during an exercise ECG stress test

The evaluation of a nonsustained wide QRS tachycardia in a life insurance applicant's exercise test presents a special challenge to the medical director because of the unpredictable and potentially lethal nature of these arrhythmias. Ventricular tachycardia accounts for up to 80% of wide QRS tachycardias in unselected populations and more than 95% of cases with a prior myocardial infarction. Malignant ventricular arrhythmias usually occur in the presence of significant structural heart disease. In this setting, ventricular arrhythmias carry a high risk of sudden cardiac death. Less commonly, ventricular tachycardia occurs in hearts that appear normal. In many such cases, however, the heart is in fact not normal, but rather has less visible abnormalities including derangements of cardiac ion channels or structural proteins. In these individuals, ventricular arrhythmias also carry a high risk of sudden cardiac death. There are, however, some ventricular tachycardia syndromes which occur in normal hearts that have a more benign prognosis.     

Frequent premature ventricular contractions

Premature ventricular contractions (PVCs) are considered normal in many circumstances but can act as markers to other cardiac disease such as cardiomyopathy and ischemic heart disease. This case is presented to illustrate frequent PVCs as a marker for serious heart disease.     

Right atrial abnormality

Occasionally, a prominent P wave is encountered in a life insurance applicant's electrocardiogram. Prominent P waves may be normal variants or alert the medical director to prognostically significant structural heart or pulmonary disease. This case study reviews the commonly used criteria for the ECG pattern of right atrial abnormality and some of the pitfalls associated with its use.     

Increased QRS voltage in the limb leads

Increased QRS voltage accompanied by repolarization abnormalities in a life insurance applicant's electrocardiogram should alert the medical director to the possibility of left ventricular hypertrophy. If confirmed, left ventricular hypertrophy or increased left ventricular mass is a strong independent risk factor for future cardiac events and all cause mortality. The use of the electrocardiogram to diagnose left ventricular hypertrophy can be helpful, but there are limitations that need to be considered. This ECG case study illustrates some of the pitfalls in the electrocardiographic diagnosis of left ventricular hypertrophy.     

Doppler echocardiographic changes found in diastolic dysfunction

Diastolic dysfunction may be associated with increased morbidity and mortality. In this article, an overview of the pathophysiology of diastolic dysfunction is discussed and the findings of Doppler echocardiography used to aid in its diagnosis are reviewed.     

The term structure of interbank risk

We infer a term structure of interbank risk from spreads between rates on interest rate swaps indexed to the London Interbank Offered Rate (LIBOR) and overnight indexed swaps. We develop a tractable model of interbank risk to decompose the term structure into default and non-default (liquidity) components. From August 2007 to January 2011, the fraction of total interbank risk due to default risk, on average, increases with maturity. At short maturities, the non-default component is important in the first half of the sample period and is correlated with measures of funding and market liquidity. The model also provides a framework for pricing, hedging, and risk management of interest rate swaps in the presence of significant basis risk.     

LVH: consequences associated with cardiac remodeling

With increased hemodynamic stress, the heart must adjust to meet the greater demands placed upon it. This adjustment frequently involves an alteration or remodeling in its structure or geometry, which augments its performance and helps to maintain adequate function under changing conditions. One of the most important forms of remodeling that the heart may undergo is an increase in muscle mass in response to a pressure or volume overload or myocardial injury. This increase in muscle mass is known as left ventricular hypertrophy (LVH). LVH is of great importance from a risk selection perspective for two reasons: it is common, and it is associated with a significant increase in both morbidity and mortality risk. Thus, it is critical that both underwriters and medical directors be aware of this form of remodeling, its causes, diagnosis and consequences.     

Optimal asset allocation under linear loss aversion

We study the asset allocation of a linear loss-averse (LA) investor and compare it to the more traditional mean-variance (MV) and conditional value-at-risk (CVaR) investors. First we derive conditions under which the LA problem is equivalent to the MV and CVaR problems and solve analytically the two-asset problem of the LA investor for a risk-free and a risky asset. Then we run simulation experiments to study properties of the optimal LA and MV portfolios under more realistic assumptions. We find that under asymmetric dependence LA portfolios outperform MV portfolios, provided investors are sufficiently loss-averse and dependence is large. Finally, using 13 EU and US assets, we implement the trading strategy of a linear LA investor who reallocates his/her portfolio on a monthly basis. We find that LA portfolios clearly outperform MV and CVaR portfolios and that incorporating a dynamic update of the LA parameters significantly improves the performance of LA portfolios.     

Stochastic inflation and government provision of indexed bonds

This paper examines the consequences of using indexed bonds as one of the government financing instruments, along with money and taxes. It is shown that open market operations between money and indexed bonds do not matter in a real sense despite their different risk characteristics. Increasing the share of indexed bonds in the government portfolio increases the volatility and the conditional mean of real rates of return on money. When provided by means other than open market operations, indexed bonds can affect the allocation of resources, but these reallocations cannot be Pareto-improving.     

U.S. Equity Investment in Emerging Stock Markets

This article examines U.S. equity flows to emerging stock marketsfrom 1978 to 1991 and draws three main conclusions. First, despitethe recent increase in U.S. equity investment in emerging stockmarkets, the U.S. portfolio remains strongly biased toward domesticequities. Second, of the fraction of the U.S. portfolio thatis allocated to foreign equity investment, the share investedin emerging stock markets is roughly proportional to the shareof the emerging stock markets in the global market capitalizationvalue. Third, the volatility of U.S. transactions in emerging-marketequities is higher than in other foreign equities. The normalizedvolatility of U.S. transactions appears to be falling over time,however, and we find no relation between the volume of U.S.transactions in foreign equity and local turnover rates or volatilityof stock returns.     

Poor R-wave progression

Poor R-wave progression is a common ECG pattern, which is often inconclusively interpreted by medical directors. Although this ECG pattern is commonly attributed to anterior myocardial infarction, it may also be caused by left bundle branch block, Wolff-Parkinson-White syndrome, right and left ventricular hypertrophy as well as by faulty ECG recording technique. Failure to make a definitive interpretation of this pattern may result in a delay or loss of business.     

Indexed bonds and revisions of inflation expectations

This paper studies the impact of revisions in inflation expectations on the prices of British inflation-indexed and conventional government bonds with a vector autoregressive model. Revisions of inflation expectations do not affect the prices of indexed bonds. The prices of conventional bonds fall with upwards revisions of inflation expectations. This suggests that indexed bonds protect investors against inflation while conventional bonds are exposed to changing monetary conditions. This is consistent with the view that indexed bonds avoid the inflation risk compensation of conventional bonds and, hence, reduce the government’s long-run borrowing costs.     

The skinny on wide QRS complexes

The presence of widened QRS complexes in a life insurance applicant's electrocardiogram may be due to such things as an intraventricular conduction defect, preexcitation syndrome, left ventricular hypertrophy, ventricular pacing, hyperkalemia and a ventricular rhythm. Clinical information and basic electrocardiogram interpretation techniques can usually narrow the differential diagnosis. Risk assessment of intraventricular conduction defects requires identification of typical electrocardiographic patterns followed by a careful search for additional electrocardiographic features, which may indicate the presence of more extensive conducting system disease and/or coexisting disease affecting the myocardium.     

American-style Indexed Executive Stock Options

This paper develops a new pricing model for American-style indexed executive stock options. We rely on a basic model framework and an indexation scheme first proposed by Johnson and Tian (2000a) in their analysis of European-style indexed options. Our derivation of the valuation formula represents an instructive example of the usefulness of the change-of-numeraire technique. In the paper's numerical section we implement the valuation formula and demonstrate that not only may the early exercise premium be significant but also that the delta of the American-style option is typically much larger than the delta of the otherwise identical (value-matched) European-style option. Vega is higher for indexed options than for conventional options but largely independent of whether the options are European- or American-style. This has important implications for the design of executive compensation contracts. We finally extend the analysis to cover the case where the option contracts are subject to delayed vesting. We show that for realistic parameter values, delayed vesting leads only to a moderate reduction in the value of the American-style indexed executive stock option.     

The impact of transaction duration,volume and direction on price dynamics and volatility

We explore the role of trade volume, trade direction, and the duration between trades in explaining price dynamics and volatility using an Asymmetric Autoregressive Conditional Duration model applied to intraday transactions data. Our results suggest that volume, direction and duration are important determinants of price dynamics, while duration is also an important determinant of volatility. However, the impact of volume and direction on volatility is marginal after controlling for duration, and the impact of volume on volatility appears to be confined to periods of infrequent trading.     

Left axis deviation

Left axis deviation is one of the most commonly encountered ECG abnormalities. Its presence should alert medical directors and underwriters to the possibility of underlying structural heart disease. Many of the causes of left axis deviation are apparent from the clinical findings. Left anterior fascicular block is one of the commonest causes of left axis deviation and has specific ECG criteria for its diagnosis.     

Mortality analysis of complete right and left bundle branch block in a selected community population

A twenty year follow up of a selected, community population with complete right and left bundle branch block is reviewed by comparative mortality analysis. In this population, where cases and controls were free of hypertension and heart disease at entry, the presence of complete right bundle branch block does not have excess mortality. Complete left bundle branch block exhibits excess total and cardiac mortality.