Malnutrition and the Heart
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I Current Review Malnutrition and the heart John G. Webb, MD Marla C. Kiess, MD, FRCPC Clifford C. Chan-Yan, MD, FRCPC Earlier concepts that the heart is spared in tante du point de vue clinique mais qu'on ne malnutrition have been shown to be incorrect. soupconne pas toujours. Une therapeutique nu- Inadequate intake of protein and energy results tritive est susceptible d'ameliorer certains mala- in proportional loss of skeletal and myocardial des souffrant de cachexie cardiaque qui devront muscle. As myocardial mass decreases, so does subir une intervention de chirurgie cardiaque et the ability to generate cardiac output; however, d'autres qu'une perte rapide de poids expose i la various compensatory factors come into play. mort subite par arythmie. Les malades hospitali- Nutritional supplementation for malnourished sds souffrent souvent de malnutrition; beaucoup patients reverses the compensatory factors and d'entre eux bEnEficient maintenant d'une thdra- may increase the short-term potential for heart peutique nutritive. Ces deux faits ont d'impor- failure. Severe cardiac debility results in poor tantes incidences sur le coeur. nutrition, which may in turn produce unsus- pected but clinically significant myocardial atro- phy. Nutritional support may play a role in he effects of specific nutritional deficiencies improving cardiac function in selected patients of vitamins and trace elements on the heart with cardiac cachexia who are being prepared are not well understood. Thiamine deficien- for cardiac surgery and in patients with rapid cy produces peripheral vasodilation,1 with resul- weight loss who are at risk for sudden death due tant high-output cardiac failure, and certain elec- to arrhythmias. Malnutrition is common in hos- trolyte deficiencies reduce cardiac contractility.2-4 pitalized patients, and many patients in hospital Selenium deficiency has been associated with a now receive nutritional supplementation; both cardiomyopathy common in certain regions of facts have important cardiac implications. China,56 and fatal selenium cardiomyopathy has been reported in patients receiving long-term par- enteral nutrition.7-9 On a cru a tort que le coeur ne souffre pas dans Of more clinical importance, however, is les etats de malnutrition. L'apport insuffisant de "protein-calorie" malnutrition - starvation. Exam- proteines et de calories determine le meme ination of the patient may suggest malnutrition on degre d'atrophie au myocarde et k la musculatu- the basis of decreased body fat and skeletal mus- re de l'appareil locomoteur. La perte de masse cle. Anthropometric assessment, including mea- myocardique diminue le debit cardiaque. Des surement of the triceps skinfold thickness and of phenomenes compensateurs entrent alors en jeu; the arm muscle circumference and calculation of leur renversement par un apport nutritif sup- the weight/height index and the creatinine/height plementaire augmente parfois, k breve echeance, index, is easily performed and permits comparison le risque de defaillance cardiaque. La faiblesse with tables of standard values.10'11 With more cardiaque elle-meme nuit a la nutrition, d'oiu advanced malnutrition, visceral proteins become possibilite d'une atrophie myocardique impor- depleted as well. When the rate of catabolism is increased, as with surgery, sepsis or severe illness, profound deficiencies of visceral proteins may From the Department of Medicine, St. Paul's Hospital and develop before a loss of body fat or skeletal muscle University ofBritish Columbia, Vancouver becomes apparent. Visceral proteins are essential Reprint requests to: Dr. John G. Webb, Division of Cardiology, in wound healing, host defences, maintenance of Toronto Western Hospital, 399 Bathurst St., Toronto, Ont. osmotic pressure and homeostatic enzymatic pro- M5T 2S8 cesses. Deficiencies of this compartment are more - For prescribing information see page 819 CMAJ, VOL. 135, OCTOBER 1, 1986 753 useful in assessing disorders than are losses of ately. However, because of the decrease in body body fat or skeletal muscle."1 Severe deficiency of size the stroke-volume index and the cardiac index visceral proteins may be suggested by low levels of remain normal or rise slightly.25'27'28 In addition, serum proteins, such as albumin and transferrin,1' systolic ejection phase indices of left ventricular or by anergy on skin testing with common anti- function, such as ejection fraction and mean rate of gens.12"13 shortening of left ventricular circumferential fibres, Anthropometric and laboratory assessments remain normal or increase slightly.27 Therefore, have suggested that 25% to 50% of patients in despite the decrease in muscle mass, the needs of hospital for more than 2 weeks suffer from some the circulation are met by these compensatory degree of protein-calorie malnutrition.14"15 Many mechanisms. disorders are associated with rapid weight loss and In starvation there is a deficiency of protein poor intake or use of nutrients. Protein-calorie substrate for maintenance of muscle protein. Me- malnutrition, although common in patients in hos- tabolism is shifted toward catabolism of muscle pital, often goes unrecognized and can have im- protein for gluconeogenesis and maintenance of portant cardiac implications. the body's other critical protein-requiring func- tions. The decrease in cardiac size is likely both a result of impaired myocardial protein maintenance Protein-calorie malnutrition and an adaptive response to decreased demands. Skeletal, myocardial and visceral proteins can Concepts of the effect of starvation on the be decreased even in obese patients. If a person heart have recently changed. The earliest report of has insufficient protein or energy intake, as with a study, by Voit,'6 in 1866, involved two cats, one intestinal bypass surgery, fasting29 or dieting,2' of which was starved for 13 days. Comparing the protein catabolism may occur to a greater degree hearts, Voit found that the heart of the starved cat than fat catabolism. Thus, obesity does not ensure was only slightly smaller, and he concluded that adequate protein stores, and obese patients may the heart is "spared" in malnutrition. This concept have low levels of serum proteins, diminished was widely accepted until it became evident from skeletal muscle and reduced myocardial mass. large autopsy studies of starved people that the amount of cardiac tissue is usually reduced in proportion to the degree of emaciation of the rest Congestive cardiac failure of the body.17 During World War II Keys and colleagues The effect of protein-calorie malnutrition on placed healthy conscientious objectors on a "Euro- the heart may not be well recognized because it so pean famine diet", consisting of small quantities of rarely results in cardiac failure. Various compensa- turnips, potatoes and cereals. After 6 months on tory mechanisms mask the effects of myocardial this low-energy, low-protein diet, the volunteers' atrophy. Notably, blood pressure, heart rate, blood average weight loss was 25%. Radiographs volume and metabolic demands for oxygen deliv- showed that the heart size was markedly de- ery decrease in the malnourished patient.17-20'23'27 creased in all dimensions, the decrease in calculat- Carbohydrate and fat intake have a marked ed cardiac volume being 70% of the decrease in direct effect on the plasma catecholamine lev- total body weight.7",8 els.30'3' The fasting patient is in a hypoadrenergic Since this landmark study a decrease in heart state, and this likely plays a role in the bradycardia size and myocardial atrophy have been widely commonly found in starved patients.3233 In Keys documented in patients with kwashiorkor,18-20 en- and coworkers' original study the average heart ergy-restricted diets,21 anorexia nervosa22 and car- rate declined steadily from 56 to only 35 beats/ diac cachexia.18,23 Pathological studies have shown min at the height of starvation.'8 In addition, atrophy and vacuolization of cardiac muscle fibres, catecholamines stimulate the production of renin, with a decrease in size and, on occasion, fragmen- angiotensin and aldosterone. Low levels of cate- tation of myofibrils.24-26 cholamines in starved patients may lead to a fall in Heymsfield and associates27 correlated the de- blood pressure through both vasodilation and crease in heart size observed radiographically with decreased sodium retention.'8'23'32'33 Starvation is a a reduction in myocardial mass demonstrated by natriuretic state; conversely, carbohydrate intake in echocardiography. Comparing a group of malnour- a fasting person rapidly decreases renal sodium ished patients in hospital with height-matched excretion.3436 In addition, a malnourished patient controls, they found by radiography a 37% de- may ingest very little salt. In mild malnutrition the crease in heart volume and by echocardiography a plasma volume per unit weight may rise, but as 22% decrease in left ventricular mass due to malnutrition becomes more severe the plasma myocardial atrophy and a 37% decrease in end- volume often falls.37 The erythrocyte mass is often diastolic volume. The decrease in heart size was decreased with malnutrition, so the total blood proportional to the decrease in skeletal muscle volume usually falls.23'37 In Keys and coworkers' bulk. studies the total blood volume had decreased an As myocardial mass decreases in starvation, average of 8.6% and the venous pressure more stroke volume and cardiac output fall proportion- than 50% at the height of starvation.'7"18'23 In 754 CMAJ,