Systole stress

Structural sarcomeric abnormalities manifested as weakened contraction and abnormal decrease in systolic stresses... 

This final section explores in a preliminary manner, an approximate method for assessing the contractile state and myocardial contractile reserve in terms of ejection fraction-afterload-preload relationships. The analysis is based on the concept of developed stress defined here to be the difference of end systolic stress and end diastolic stress. 

The term afterload has taken on several meanings in the literature and these include mean systolic stress, peak systolic stress, stress at aortic valve opening, mean aortic pressure and more recently, end systolic pressure and end systolic stress. The variety of definitions is simply due to the fact that afterload varies continuously throughout ejection. 

Figure 17. Ejection fraction versus afterload and preload relationships. Left. Ejection fraction-end systolic stress relations at constant levels of end diastolic volume. The optimal relation corresponds to the absolute maximum value of developed stress. Right. Ejection fraction - end diastolic stress relations at constant levels of afterload. These relationships enable one to compare the contractile states between different ventricles.

Carabello BA, Nolan SP, McGuire LA (1981) Assessment of preoperative left ventricular function in patients with mitral regurgitation Value of the end-systolic stress-end-systolic volume ratio. Circulation 64 1212-1217... 

Arteriolar and venous tone (smooth muscle tension) both play a role in determining myocardial wall stress (Table 12-1). Arteriolar tone directly controls peripheral vascular resistance and thus arterial blood pressure. In systole, intraventricular pressure must exceed aortic pressure to eject blood arterial blood pressure thus determines the systolic wall stress in an important way. Venous tone determines the capacity of the venous circulation and controls the amount of blood sequestered in the venous system versus the amount returned to the heart. Venous tone thereby determines the diastolic wall stress. 

Epidemiologic, experimental, and in vitro mechanistic data indicate that lead exposure elevates blood pressure in susceptible individuals. In populations with environmental or occupational lead exposure, blood lead concentration is linked with increases in systolic and diastolic blood pressure. Studies of middle-aged and elderly men and women have identified relatively low levels of lead exposure sustained by the general population to be an independent risk factor for hypertension. In addition, epidemiologic studies suggest that low to moderate levels of lead exposure are risk factors for increased cardiovascular mortality. Lead can also elevate blood pressure in experimental animals. The pressor effect of lead may be mediated by an interaction with calcium mediated contraction of vascular smooth muscle, as well as generation of oxidative stress and an associated interference in nitric oxide signaling pathways. 

Many clinical observations indicate that neurogenic factors in some way influence the development and maintenance of essential hypertension. It has long been recognized that stressful situations may induce marked increases in both systolic and diastolic pressures which persist for varying periods of time (21, 38), and that hypertensives tend to have a characteristic type of personality (2, 99. Such individuals usually exhibit important components of repressed antagonism and anxiety. They do not find emotional outlets in overt acts, but rather their emotions are expressed through an increased activity of the sympatho-adrenal system with a consequent increase in blood pressure. Relief of psychic tension frequently produces salutary effects in these patients. Individuals who show hyperactive sympathetic vasomotor reflexes (as measured by the cold pressor test) are much more prone than the average individual to develop hypertension in later life (57). 

Fig. 12.1 Concentric and eccentric cardiac remodeling. In response to a systolic load, newly formed sarcomeres will be assembled in a parallel fashion leading to an increase in myocyte cell width. This mode of sarcomere assembly will result in a concentric pattern of cardiac hypertrophy characterized by an increase in wall thickness and reduction in chamber volume. In contrast, in response to a diastolic load, newly formed sarcomeres will be assembled in an in series pattern leading to an increase in myocyte cell length. This mode of sarcomere assembly will promote an eccentric pattern of cardiac hypertrophy characterized primarily by an increase in chamber volume. However, a modest increase in wall thickness will also occur because of the secondary increase in systolic wall stress associated with eccentric remodeling.

Quebec City from 1991 to 1993 and followed up with 84 percent of the participants seven and a half years later to assess the impact of job strain. Compared with a similar group of workers not exposed to the same levels of work-related stress, the subjects who were under continuous job strain had an increase in systolic blood pressure equivalent to that expected from aging and sedentary behavior. Put in other words, the job stress those workers experienced was equal in its ill effects to aging seven and a half years or being sedentary for that period of time. 

I nearly forgot to mention the most important weapons to lower blood pressure and prevent cardiovascular disease, heart attack, and stroke. You ve read about ways to cope with stress, lose weight, quit smoking cigarettes, become more physically active, improve your diet, and counterbalance salt and sodium. You ve learned about natural, safe, and clinically documented effective supplements that can dramatically lower both systolic and diastolic blood pressure. Those supplements weren t even available when I was first inspired to write this book after studying newly published blood pressure guidelines in 2003. So what s missing ... 

In one study 38% of patients undergoing dobutamine stress echocardiography developed hypotension. Increases in blood pressure are more in hne with what one would expect. Although dobutamine does not as a rule cause a marked increase in systolic blood pressure in normotensive patients, hjrpertensive patients can develop marked systolic hypertension during an infusion of the drug. When stress echocardiography with dobutamine is performed in subjects who prove to be entirely healthy, an audible Still s-like vibratory systolic ejection murmur is nevertheless produced. 

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