heart sound is indistinct (though loud) because of the overdistension and slow contraction of the ventricle. Aortic Stenosis. — In stenosis of the aortic orifice the blood is forced from the ventricle under increased pressure through a very narrow opening, and a sound is produced similar to that described in mitral stenosis. It occurs, of course, during ventricular contraction, and is a systolic murmur. The sounds produced by the lesions above mentioned are propagated along the direction of the blood current and as the valves themselves all lie within a very small area the sounds are best differentiated by listening to them at the suburban heart points, to which they are transmitted. Thus the sounds and their significance may be classed as follows: (1) Systolic murmur, heard best at apex, indicates mitral insufficiency. <Callout type="important" title="Important">This can lead to high venous pressure and dropsy.</Callout> (2) Pre-systolic murmur, heard best at apex, indicates mitral stenosis. (3) Diastolic murmur, heard best at aortic arch, indicates aortic insufficiency. (4) Pre-diastolic murmur, heard best at aortic arch, indicates aortic stenosis. Pulmonary Lesions. — The valves of the right heart are subject to precisely the same conditions as here described, and present a corresponding set of sounds, but their occurrence is so rare as to demand no special attention.
Haemic Murmurs. — Similar dynamic conditions to those of valvular insufficiency may be brought about by abnormalities of the blood, which decrease its density, and murmurs are frequently thus produced. Particularly is this the case in anemia. The sounds are neither so loud nor so constant as in valvular lesions, and are called haemic, or functional murmurs.
Accentuation. — Anything which augments the force of the heart beat increases the muscular impetus and therefore accentuates the first sound of the heart. We have already seen that hypertrophy is the chief of these influences; exercise, emotions, and certain drugs also have this effect, and it is a not infrequent practice among diagnosticians to administer strychnia in order to augment the first sound and bring out suspected abnormalities. The second sound, depending upon the closure of the semilunar valves, is accentuated by anything which increases the intra-arterial pressure, and its accentuation is pathognomonic of diseases in which peripheral resistance is increased, of which arterio-sclerosis and kidney diseases are familiar illustrations. Accentuation of second sound is, of course physiologic in old age, because of atheroma of the vessels. Accentuation may occur from the causes described in any of the valves separately, which together make up the respective sounds. These separate accentuations must be diagnosed by auscultating at the outlying points of sound transmission for the separate valves.
Reduplication of the heart sound is due to the asynchronous occurrence of the events which produce it. In the first sound, of course, the valvular element is the only one which can be reduplicated and as this element is completely overshadowed by the muscular element, its reduplication is practically unrecognizable. Eeduplication of the second sound is not an infrequent symptom and is usually due to some pathological condition of the coronary arteries. The two sides of the heart, being unequally nourished, do not functionate synchronously; the semilunar valves close asynchronously, and give a double sound. The same phenomenon results from an unequal tension in the two ventricular cavities, due to valvular leaks and stenoses. Myocarditis and Patty Degeneration reduce' the force of the muscle contraction and therefore make the first sound weak and indistinct. The second sound, by contrast, seems accentuated; but in cases of high blood pressure from other causes, the second sound may of course be genuinely reduplicated.
The Cardiac Cycle. — At the instant that the wave of muscle contraction begins, at the mouth of the pulmonary veins, the left auricle is full of oxygen-ated blood which has been poured into it by the pulmonary veins. As the contraction passes over the auricle its capacity lessens, the pulmonary valve is closed by the pressure of the blood, and the latter is driven forward through the auricula-ventricular valve into the ventricle. The contraction wave now passing over to the ventricle, its capacity is reduced, the pressure closing the mitral valve and driving the blood out into the aorta. Meantime the auricle has relaxed and refilled with blood from the pulmonary veins. The blood being forced into the aorta distends its walls, which, however, promptly recoils and closes the semilunar valves. This ends the cycle. A precisely similar cycle of events takes place in the right auricle and ventricle, except that the blood received from the venae cavae is venous blood, and is pumped by the ventricle into the pulmonary artery.
Mitral Insufficiency.— Thus, if the mitral valve leaks, at each ventricular contraction a portion of its contained blood is forced back into the auricle and an insufficient quantity pumped into the aorta. The auricle is then receiving blood both from the venae cavae and from the ventricle and becomes much distended, and the tendency is for a backward stasis of circulation. However, the auricular muscle responds to this demand by hypertrophying (compensatory hypertrophy) and contracting more forcibly. In time, of course, hypertrophy can no longer make up for the increased work, and compensation fails. The result, as one would suppose, is backward stasis in the veins, high venous and low arterial pressure, the former causing dropsy and C02 poisoning, the latter insufficient oxygenation, shortness of breath and general atony.
Aortic Insufficiency. — Leakage of the semilunar valve produces, by the same dynamic process, a compensatory hypertrophy of the ventricle and eventually backward stasis. Mitral Stenosis. — Stenosis of the mitral orifice, although a reverse condition to insufficiency, produces the same results by a somewhat different mechanism. Here the narrowness of the opening imposes a systolic pressure upon the auricle, which is compensated by auricular hypertrophy, later producing backward stasis. Aortic Stenosis. — Narrowing of the aortic opening operates upon the ventricle precisely as vertical stenosis does upon the auricle, with the same backward train of events.
Leakage and Stenosis of the Right Heart. — Insufficiency and stenosis of the valvular mechanism of the right heart produces a set of conditions precisely corresponding to those described for the left heart. In these cases, however, the pulmonary circulation is the first to feel the effects of backward stasis due to failing compensation, and respiratory difficulties are the earliest and most direct results.
Fortunately, as already stated, they are much rarer, owing to the less opportunity for functional derangement than in the systemic circulation. The Coronary Arteries. — Another source of interference with the cardiac cycle is frequently seen in a lesion of the coronary arteries. In order to properly carry out their function all the heart muscles must themselves be regularly and adequately supplied with nutrient blood, and any condition of the coronary arteries (e.g., sclerosis, embolism, thrombosis) will produce a disturbance in the performance of the heart cycle. Sudden stoppage of the heart (in diastole, of course) often results from this cause, which is also thought to be the explanation of the phenomenon known as angina pectoris.
Intrapulmonary Pressure. — Any condition producing an increase of intrapulmonary pressure will, if continued long enough, embarrass the right ventricle, and bring about its hypertrophy, with eventual failure of compensation and fatal stasis. Emphysema is a notable example of this. (See Respiration.) Systemic Pressure, long continued, such as is caused by chronic Blight's disease, diabetes, arterio-sclerosis, etc., will bring about the same train of results in the left heart.
Tonicity and Maximal Contractions of Heart Muscle. — The heart muscle, like the skeletal muscles, is in a constant state of more or less contraction; unlike the skeletal muscles, however, it appears to possess this tonicity independently of its connection with any nerve centre. It exhibits a further dissimilarity to skeletal muscles in that its contractions are always maximal, i.e., when it contracts at all it contracts to the farthest limit of its contractility.
Neurology of Heart. Nervous Control of the Heart.— Although the origination of the heart's action is independent of the central nervous systems, its performance is largely-modified by two sets of efferent neurons. One, the vagus, is received from the undulla, and inhibits the action of the heart muscle, slowing its beat, and can- celling its tonicity, so that when the heart (as occasionally happens) is stopped by stimulation of the vagus, it is arrested in exaggerated diastole. The other set, the accelerators, come from the sympathetic chain, and augment the velocity of the beat.
Cardio-Inhibitory Function. — Stimulation of the vagus nerve inhibits the heart's beat and cancels the tonicity of its muscle, finally arresting it in exaggerated diastole. The activity of this nerve also lessens the conductivity of the heart muscle, causing a condition known as heart block, i.e., where the contraction wave does not regularly pass over from the auricle to the ventricle, so that there are two beats of the former to one of the latter. Experiment proves that the fibres of the vagus reach and influence both the auricles and ventricles direct, but their distribution to and influence upon the ventricles are less than to the auricles, while with the accelerator nerves the reverse is the case.
Heart Block. — In this condition, already described, the beat of the ventricles is always in excess of that of the auricles, because of the distribution of accelerator and inhibitory influence above referred to, and also because of interference with the conductivity of the heart muscle described above.
Reflex Inhibition. — The cardio-inhibitory action of the vagus may be called into play reflexly by stimulation of various sensory neurons, notably by the stimulation of those sensory fibres of the vagus which are distributed to the thoracic and abdominal viscera. The cardio-inhibitory centre is in a constant state of tonicity, acting as a continual automatic drag on the heart, preventing it from beating as rapidly as it would otherwise do, and this tonicity of the centre is doubtless a reflex phenomenon, mediated apparently by various sensory impulses.
Accelerators Balance. — The accelerator nerves, derived from the sympathetic, whose influence is precisely the opposite to that of the vagus, are also capable of being called into action by reflex means. Thus it seems that the velocity of the heart is normally regulated by the influence of two antagonistic nerve-currents, one accelerating and the other inhibiting its beat.
Digestion. Mastication is performed by means of the digastric muscle, which depresses the jaw; the masseters, temporals, and internal pterygoids, which raise it; and the external pterygoids, which move the jaw laterally (grinding).
Innervation. — All the muscles of mastication receive their motor power by way of the inferior maxillary branch of the fifth cranial nerve.
Bulbar Paralysis. — One of the earliest manifestations of bulbar paralysis is dysarthria, or difficulty of jaw movement, due to involvement of the root of the fifth nerve. The lesion of this particular part is probably no earlier in fact than that of other bulbar areas, but its impairment is noticed first.
Later, there is complete inability to masticate. Imperfect Mastication, from whatever cause, sends the food to the stomach imperfectly prepared, thus delaying its passage through that organ and giving rise to fermentation, flatulence, and indigestion, and is, in these days of hurry, a fertile cause of stomach trouble.
Salivary Glands. — These consist of the parotid, submaxillary and sublingual glands, all of which belong to the type of tubular glands. The Saliva is a colorless viscid liquid of alkaline reaction and a specific gravity of about 1.003. Its principal ingredient is an enzyme called ptyalin, which reacts upon starch to produce a diastase. It also contains some proteid maltose, and sodium potassium and calcium salts. In solution saliva contains carbon dioxide, the product (and measure) of the metabolic activity of the glands.
The secretion contributed by the parotid gland is richer in ptyalin and poorer in mucin than the secretion of the other two; the latter is given a more alkaline reaction than the parotid secretion. Ptyalism is an excessive secretion of saliva. It is rarely, if ever, a primary complaint, but depends upon some other pathological condition, and the saliva is usually altered in character as well as increased in quantity.
Inflammations of the Mouth and Throat, unless accompanied by a high temperature, are always attended by an increased flow of saliva, due partly to vasodilator conditions and partly to increased reflex stimulation. In such cases it is usually acid in reaction, because of the increased absorption of CO2 and other metabolic acid products.
Pregnancy is attended by a more or less degree of ptyalism. Mercurial Ptyalism is due to hyperstimulation of all the salivary glands by the drug. In Fevers the watery part of the saliva is rapidly absorbed by the mucous membrane to compensate for the general anhydrous condition of the tissues and the secretion is therefore thick and viscid, and feels dry and sticky. The same condition is found, and for the same reason, in Diabetes and certain forms of Nephritis.
The reaction becomes acid in Fevers, Diabetes, Gout, Rheumatism and Nephritis, because of the absorption of metabolic acid products, chiefly CO2 in the first two diseases and uric acid in the others. In gouty subjects the acidity is sometimes so high as to erode the chin and corners of the mouth.
Innervation. — The salivary glands receive their stimuli both from the cerebral centres through the chorda tympani and from the sympathetic by way of the cervical ganglia. Experiment shows that cerebral stimulation produces a thin, watery secretion, poor in solids, whereas sympathetic irritation causes the secretion of a viscid thick substance, rich in solids.
The present theory is that the cerebral fibers mediate the purely secretory element in the function, i.e., the osmotic filtration of the gland, while the sympathetic performs a trophic part, increasing the metabolism of the cells and producing organic products.
Vaso-Motor Influences. — In addition to the above nervous supply, the chorda tympani carries vaso-dilator fibers, whose stimulation dilates the capillaries of the glands, and the sympathetic carries vaso-constrictor fibers whose stimulation constricts the capillaries.
Dry Mouth is a condition, described first by Hutchinson, in which the secretion of the saliva is inhibited as the result of a central nervous disturbance. The parotid glands become hard but painless. In fevers the watery portion of the saliva is rapidly absorbed by the mucous tissues to compensate for the general anhydrous condition of the body, and the saliva is therefore thick and viscid.
Reflex Mechanism. — The function of the salivary glands is a reflex one, whose centre is in the medulla. It receives afferent stimuli from numerous sources, chief among which, of course, are the sensory of the tongue and palate, by means of the glossopharyngeal and lingual nerves. The stomach by means of the vagus, and the nose by means of the olfactory nerve, also furnish afferent stimuli, and that the cerebral centres may both directly stimulate and inhibit the salivary centre is evidenced by the well known effects of various emotions and ideas upon the secretion.
(Watering at the mouth and parched throat, due to longing and fear respectively.) Experiment demonstrates that the efferent part of this reflex is mediated wholly by the chorda tympani, the sympathetic of itself being ineffectual to do so.
Stomatitis and Glossitis. — Undoubtedly the ptyalisms of inflammations of mouth and tongue are partly due to irritation of the afferent fibers of the glosso-labio-laryngeal nerves. Gastric Ptyalism, as seen in catarrhal gastritis, gastric ulcer, before vomiting, etc., are due to stimulation of the afferent fibers in the gastric branch of the vagus.
Deficient Saliva is one of the results of imperfect and hasty mastication, because the latter act is one of the chief exciters of the salivary reflex. The Function of the Saliva is both mechanical and chemical. Mechanically, it moistens the food, enabling it to be conveniently masticated and swallowed, and dissolves certain parts of the material so as to act upon the taste buds. Chemically its principal function is to convert the starch in the food into dextrin and sugar by means of its diastase, ptyalin. This is supposed to be accomplished by the starch molecules taking up water and splitting into more elementary molecules. The reaction is not completed in the mouth, but the food, thoroughly mixed with saliva, passes into the stomach and remains there some little time untouched by the gastric juices, while the diastase finishes its work.
Heat increases the activity of the salivary process up to
Key Takeaways
- Identify heart sounds and murmurs to diagnose cardiac conditions.
- Understand the significance of different types of murmurs in diagnosing specific valve issues.
- Recognize the importance of auscultation for accurate diagnosis.
Practical Tips
- Practice listening to your own heartbeat regularly to familiarize yourself with normal heart sounds.
- Use a stethoscope when available, but be able to identify key heart sounds by touch if necessary.
- Look for signs of compensatory hypertrophy and stasis as indicators of long-term cardiac issues.
Warnings & Risks
- Be cautious of administering drugs like strychnia without proper medical training; it can cause severe side effects.
- Avoid overreliance on auscultation alone, as other factors may contribute to heart sounds and murmurs.
- Recognize that some conditions, like aortic stenosis, are rare but potentially life-threatening.
Modern Application
While the techniques described in this chapter are rooted in historical practices, the principles of cardiac diagnosis remain relevant. Modern tools such as ECGs and echocardiograms have improved accuracy, but understanding heart sounds and murmurs is still crucial for quick triage in survival situations where advanced medical equipment may not be available.
Frequently Asked Questions
Q: What are the key differences between mitral stenosis and mitral insufficiency?
Mitral stenosis involves a narrow opening of the mitral valve, leading to increased pressure during ventricular contraction. Mitral insufficiency occurs when the valve leaks, causing backflow into the left atrium and reducing the amount of blood pumped into the aorta.
Q: How can you differentiate between systolic and diastolic murmurs?
Systolic murmurs occur during ventricular contraction (systole) and are often associated with valve stenosis. Diastolic murmurs happen during ventricular relaxation (diastole) and typically indicate valve insufficiency.
Q: What are the potential long-term consequences of mitral valve leakage?
Mitral valve leakage can lead to compensatory hypertrophy, which over time may fail. This results in backward stasis, high venous pressure, and low arterial pressure, causing symptoms like shortness of breath and general atony.