Disorders of Cardiovascular System | Humans | Medical Science

Here is a list of disorders of cardiovascular system.

Disorder # 1. Atrial Fibrillation:

Pathophysiology:

Atrial fibrillation is observed in many cardiac disorders. Atrial ectopic rate is 350 to 600 per minute. There is varying degree of atrioventricular block. Ventricular response being totally irregular. It was believed formerly that circus movement may cause this irregular rhythm. Atria might have several discharging sites, which may form irregular impulses.

Aetiology:

Atrial fibrillation is observed with under-mentioned conditions:

(1) Rheumatic heart diseases especially mitral stenosis

(2) Ischaemic heart disease

(3) Hypertensive heart disease

(4) Thyrotoxicosis

(5) Pericarditis

(6) Cardiomyopathy

(7) Idiopathic or lone fibrillation

(8) Miscellaneous conditions like chronic lung disease, or mediastinal tumours.

(9) Post-operatively – after thoracic surgery

(10) Congenital heart disease like A.S.D.

Pathophysiology:

Atrial fibrillation is observed in many cardiac disorders. Atrial ectopic rate is 350 to 600 per minute. There is varying degree of atrioventricular block. Ventricular response being totally irregular. Usually AV node prevents ventricular rate to go higher than 200 min, generally much slower than auricular rate.

However, ventricular rhythm will be slow and regular during atrial fibrillation, if there is pre-existing complete AV block. It was believed formerly that circus movement may cause this irregular rhythm. Atria might have several discharging sites, which may form irregular impulses.

Clinical Features:

The pulse is irregularly irregular. Though usually fast, it may be slow depending upon degree of AV block. On auscultation heart rate is irregular and faster. Many weak contractions cannot produce radial pulse and there is a difference between heart rate and pulse rate. This is called pulse deficit.

In jugular veins, there is no evidence of atrial contractions i.e. ‘a’ waves are not seen. First heart-sound varies in intensity. Second sound may or may not be heard. In mitral stenosis systolic murmurs are heard but presystolic rumble of mitral stenosis is absent because of ineffective atrial contractions, ECG shows:

(1) Normal P waves are absent;

(2) Fibrillary waves are seen, replacing ‘P’ waves;

(3) Irregularly placed QRS complexes have varying ‘R’ amplitude.

Diagnosis:

Pulse-apex deficit is usually diagnostic; multiple extrasystoles may mimic atrial fibrillation. Here though pulse-apex deficit is present it is not usually high, multiple ectopic beats may disappear after exercise. Atrial flutter needs to be ruled out. Jugular veins show flutter waves.

In partial heart block, dropped beats may create confusion but ‘a’ waves can be observed in jugular veins. ECG is diagnostic.

Treatment:

Aetiological factor e.g. thyrotoxicosis if discovered should be treated. However, main intention should be to control ventricular rate by digitalisation. However, if adequate digitalisation fails to control heart rate, beta-blocker or calcium channel blocker in small dose can be administered. Good old drug quinidine is replaced nowadays with recently available calcium-blockers or beta-blockers.

In chronic rheumatic heart disease, if there is persistent auricular fibrillation, anticoagulants should be used to prevent embolism. When above mentioned drug regimen fails electrical defibrillation is attempted. Due to risk of embolism, anti-coagulants are given before ‘electroversion’.

Disorder # 2. Atrial Flutter:

In atrial flutter, atrial contractions are both co-ordinated and regular. The ventricles are discharged by every second, third or fourth impulse, thereby producing varying types of block e.g. 2: 1, 3:1, or 4: 1.

Aetiology:

Aetiological factors are more or less the same as in atrial fibrillation. Sometimes it is idiopathic as no cause can be detected.

Clinical Features:

The heart rate is faster and regular. Atria may contract around 300 times a minute. But due to varying degrees of block at A.V. level, ventricular contractions may be 75 to 150 per minute, depending upon the degree of block. Carotid sinus pressure may reduce the rate to half but effect is temporary. Flutter waves may be seen in jugular venous pulse. In ECG ‘saw-tooth’ appearance of atrial waves with ventricular response at alternate or every third or fourth beat settles the diagnosis of atrial flutter.

When there is 2: 1 conduction in atrial flutter, it may be mistaken for sinus tachycardia. Leads II, AVF, V₁, V₂ and V₆ should be carefully inspected to detect F waves.

Treatment:

Treat the aetiological factor. Ventricular rate should be controlled by digitalisation which converts atrial flutter into fibrillation. Withdraw digitalis at this stage abruptly and sinus rhythm may be restored or flutter may continue with increased degree of AV block.

More rapid and safe way is direct-current QRS-synchronised shock, when electroversion is planned, anticoagulant should be administered one week before cardioversion to minimise chances of embolism.

Propranolol may be used to control rapid rate after digitalisation. In some selected cases atrial pacing is done.

Disorder # 3. Wolff-Parkinson-White Syndrome:

In the Wolff-Parkinson-White syndrome (WPW syndrome), one ventricle may get activated earlier. This is supposed to be through an accessory bundle (bundle of Kent). As conduction is accelerated, so also it is known as accelerated conduction syndrome or pre-excitation syndrome. Though usually benign, it forecasts the possibility of on-coming atrial arrhythmias, especially paroxysmal tachycardia, predominantly affecting males in all age groups; diagnosis is only by E.C.G. (short PR interval, lengthened QRS duration with initial delta wave).

The syndrome is classified into two types:

Type A and type B depending on the shape of V₁, complex. In A type, ventricular complex is prominently positive where the bundle of Kent is on the left side of the heart and in type B it is on the right side and ventricular complex is negative. This explanation, however, is not accepted by all.

Two types of arrhythmias may occur in W-P-W syndrome i.e.:

(1) Paroxysmal supra-ventricular tachycardia

(2) Atrial fibrillation.

It should be remembered that digitalis though useful in atrial fibrillation is dangerous in W-P-W syndrome as the bundle of Kent will allow rapid contraction of auricular impulse to ventricle causing dangerous ventricular tachycardia.

Lown-Ganong-Leaving Syndrome:

The typical picture also consists of short PR in interval with normal QRS without any slurring. There is tendency to paroxysmal tachycardia. In this syndrome also there is a duplicate path of conduction between atrium and bundle of His, a by-pass of AV node. As the by-pass directly goes to Bundle of His, QRS has no delta wave as in WPW syndrome.

Disorder # 4. Aortic Stenosis:

Aetiology:

Rheumatic:

Chronic rheumatic endocarditis may cause fusion of the commissures of aortic valve resulting in stenosis.

Congenital:

It is also a common cause in adults the valve being bicuspid in most instances. Physical signs are trivial in childhood and adolescence. Subsequent calcification and distortion in middle age produce significant symptoms.

Degenerative:

In the elderly, degenerative changes in the aortic valve with sclerosis and calcification may produce signs of aortic valve stenosis in absence of significant obstruction.

Hyper-Lipoproteinaemia:

Hyper-Lipoproteinaemia (Type II and III) is a rare cause of aortic stenosis.

In addition to stenosis at the level of the valve there may be obstruction above the level of the valve i.e. congenital supravalvular stenosis or below the level of valve i.e. subvalvular stenosis. In subvalvular stenosis, a localised fibrous ring produces the obstruction or the obstruction may arise from septal hypertrophy in hypertrophic obstructive cardiomyopathies (IHSS).

Haemodynamics:

Haemodynamic consequences occur when the orifice of the aortic valve which is normally above 3 cm² is reduced to around 50 per cent of its size. The stenosis causes pressure load on the left ventricle which undergoes hypertrophy (concentric hypertrophy). The end-diastolic pressure in the left ventricle increases because of reduced myocardial compliance with consequent rise of pressure in the left atrium. Pulmonary congestion then begins to appear.

In course of time the stenosed valve calcifies irrespective of the aetiology. Calcification may involve coronary ostia. Although in the majority of cases calcification is-confined to the aortic valve, it may spread downwards to involve the anterior leaflet of the mitral valve or A-V node. The latter condition may give rise to prolonged A-V conduction or even complete A-V block. As a result of ejection of blood through a stenosed orifice like a jet, there is dilatation of ascending aorta.

Clinical Features:

Symptoms:

(1) Breathlessness may not be an early symptom. It results from elevated left atrial pressure consequent upon increased left ventricular end-diastolic pressure. It starts as shortness of breath on exertion and may progress to orthopnoea. Paroxysmal nocturnal dyspnoea occurs in the late stage of the disease.

(2) Angina pectoris is a common symptom and may occur even in presence of normal coronary arteries. It is, however, clinically indistinguisable from angina resulting from coronary arterial disease. Angina in aortic stenosis has been attributed to (a) low mean aortic pressure, (b) jet effect which interferes with coronary filling, (c) discrepancy between the flow and needs of the hypertrophied left ventricle, and (d) rarely coronary embolism.

(3) Syncope – Occurs in about 20 per cent of cases. It results from exercise induced vasodilatation in presence of a fixed cardiac output. It may be the result of transient episode of A. V. block or the result of locking of the valve due to calcium deposit.

(4) Dizziness – It is most frequent when the patient is standing. Poor cerebral perfusion caused by low cardiac output and orthostatic mechanism, contributes to this symptoms.

(5) Sudden death – May occur due to combination of above mechanism.

Physical Signs:

Pulse is of small volume and in severe cases may be plateau in form. Anacrotic notch is not always felt in radial pulse. The carotid pulse in the neck is slow rising with a reduced amplitude and an early notch in the upstroke may be felt. A thrill may also be palpable over the carotid.

The jugular venous pulse and pressure are normal but a small a’ wave may frequently be seen. It probably results from Bernheim effect, the hypertrophied septum reducing the cavity of the right ventricle.

The apical impulse is sustained heaving in type due to left ventricular hypertrophy. A thrill is usually palpable over the aortic area. On auscultation, the first sound is normal and is occasionally preceded by an S₄ (fourth heart sound) due to atrial contraction. The second sound is single when the valve is calcified due to loss of the aortic component.

In young patients, where the cusps are mobile, aortic component is audible but delayed. This is described as ‘reversed splitting’. The characteristic murmur of aortic valve stenosis is a rough ejection systolic murmur audible over the base. The murmur is conducted along the carotid and is also audible over the apex. The ejection murmur cannot start until aortic valve opens at the end of isometric contraction phase.

So it begins clearly after the first heart sound. The murmur ceases when the left ventricle starts relaxing that is appreciably before the aortic valve closure (2nd sound). Therefore, the murmur is midsystolic and from the phonocardiography appearance described as ‘diamond’ shaped murmur. Blood pressure is usually normal at rest.

ECG:

Shows left ventricular hypertrophy and strain pattern. Sinus rhythm is usual and presence of atrial fibrillation indicates co-existing mitral valve disease. A normal electrocardiogram, however, does not preclude aortic valve stenosis.

Chest X-Ray:

The heart is often of normal size, but has a rounded left contour indicating left ventricular hypertrophy. The ascending aorta is usually prominent owing to post-stenotic dilatation produced by the jet effect. When heart failure develops the heart size is enlarged and signs of pulmonary congestion appear in the lung fields. Left lateral view or left oblique view helps not only in assessing in left ventricular size but also in identification of aortic valve calcification.

Special Investigations:

Exercise Test:

This helps in assessing the patient’s functional capacity. If the patient’s ECG and blood pressure can be monitored and supervised, he may be exercised to the limit of anginal pain, dyspnoea or exhaustion. Appearance of arrhythmia or a tendency to fall of blood pressure will necessitate termination of exercise test.

Cardiac Catheterisation:

It is performed for measurement of pressure gradient across aortic valve, cardiac output and for angiocardiographic studies. The left ventricle can be approached by brachial arteriotomy or by femoral puncture through Seldinger’s technique or by transeptal puncture via right and left atria. The severity of the stenosis can be estimated from the systolic pressure gradient between left ventricle and aorta. Resting cardiac output is usually normal in absence of heart failure.

Left ventricular angiogram helps in visualising the anatomy of the stenosed valve and also in assessing the contractibility of the myocardium. It can be combined with selective coronary angiography, particularly if there is any angina.

Echocardiography:

Helps in estimating the thickness of cusps and of the left ventricle cavity and wall dimension. It also gives an impression of the contractibility.

Treatment:

Patients with physical signs of aortic stenosis without any subjective symptoms and who have a normal working capacity do not require any treatment nor any haemodynamic investigation. Prophylactic measures against infective endocarditis and secondary prevention of rheumatic recurrences are all that would be necessary. A clinical assessment including exercise test at one yearly interval has been recommended. The patient should be advised to avoid sustained strenuous physical exercise.

Appearance of symptoms and reduction of physical working capacity would necessitate haemodynamic evaluation in a cardiac laboratory. Heart failure should be treated with bed rest, digitalis and diuretic with potassium supplements. Angina pectoris usually responds to glyceryl trinitrate and prophylactic use of isosorbide-dinitrate, beta-receptor blocking agents and calcium antagonists.

It is important to bear in mmd that glyceryl trinitrate and vasodilators may occasionally produce syncope from a fall of blood pressure and beta receptor blocking agents should be avoided in presence of heart failure. Surgical treatment should comprise of commissurotomy provided the cusps are elastic and not calcified. Re-stenosis and post-operative incompetence may occur subsequently in many cases and eventually require valve replacement.

Valve replacement is carried out using either artificial valve prosthesis, homografts or frame supported porcine valves.

Disorder # 5. Aortic Regurgitation Aortic Valve Incompetence:

Aetiology:

(1) Rheumatic fever — is considered to be the most common cause of aortic incompetence.

(2) Subacute infective endocarditis – may affect the congenital bicuspid valve or a mildly incompetent aortic valve. The incompetence resulting from infective endocarditis is usually acute.

(3) Syphilis – accounts for only a small number of cases although it used to be major cause in the first half of this century.

(4) Degenerative – Some authorities believe that atheromatous changes can cause incompetence.

Rare causes include:

(1) Marfan’s syndrome – Here the cusps are redundant and chordae are lax and result in incomplete apposition of cusps.

(2) Sero-negative arthritides – e.g. Ankylosing spondylitis and Reiter’s syndrome.

(3) Rheumatoid arthritis and SLE rarely produce incompetence of aortic valve.

(4) Dissecting aneurysm of aorta with or without Marfan’s syndrome.

(5) Coarctation of aorta.

(6) Congenital bicuspid valve — Usually produces trivial leak, but acute aortic incompetence may result following infective endocarditis.

(7) Ventricular septal defect associated with prolapse of aortic valve.

Still rare causes are:

(1) Traumatic rupture of aortic cusp

(2) Pseudoxanthoma elasticum

(3) Methysergide poisoning

(4) Congenital aneurysm of the sinuses of Valsalva

(5) Mucopolysaccharoidosis – like Hurler’s syndrome, Morquio’s syndrome, etc.

Haemodynamics:

Since the aortic valve is incompetent only part of the ventricular output reaches the periphery and the remainder regurgitates back into the heart. This results in volume overload of the left ventricle which dilates and later undergoes hypertrophy. The myocardial compliance is reduced and end-diastolic pressure in the left ventricle increases causing a rise in left atrial pressure and development of pulmonary congestion.

The stroke volume of the left ventricle is increased and the ejection phase is shortened. In early systole a large quantity of blood is quickly ejected into relaxed arteries because of low diastolic pressure. The low diastolic pressure is due to both aortic reflux and peripheral vasodilatation (Oram).

Clinical Features:

Symptoms:

Dizziness and palpitation are the common presenting symptoms. Throbbing sensation in the chest and/or head may result from rapid ejection of a large stroke volume. Palpitation is more intense in supine position. The throbbing sensation may induce anxiety and may produce other symptoms like fatigue, chest pain and difficulty in breathing.

Dyspnoea:

Usually results from left ventricular failure and may be progressive.

Angina Pectoris:

Is less common than in aortic stenosis. The low aortic diastolic pressure may contribute to an insufficient diastolic filling of coronary arteries. A raised intracavitary pressure during diastole may also interfere with coronary diastolic flow. Compared to increased, myocardial demands for oxygen of the dilated and hypertrophic left ventricle, the available supply is reduced due to poor coronary perfusion resulting in angina. Angina is more frequent in aortic incompetence of leutic origin and is usually more troublesome during the night.

Signs:

The pulse is of high amplitude and in the radial arteries produces a “water hammer” or collapsing pulse as a result of sharp pressure rise followed by an equally rapid fall in pressure resulting from regurgitation of blood back into left ventricle.

Capillary pulsation may be observed in the nail beds by applying light pressure on the tips. It can also be demonstrated in the inner aspect of the lower lips by pressing with a glass slide. It can also be detected in the retinal arteries by observing the variation of the small gap where the retinal arterioles and venules are running close to each other.

It is important to remember that retinal veins pulsate but not the arterioles. Palpation of the precordium reveals displacement of the apical impulse downwards and to the left as an evidence of left ventricular enlargement. The apical impulse Is forceful resulting from myocardial hypertrophy and a large stroke volume. Only in severe regurgitation a diastolic thrill is palpable along left sternal edge.

Auscultation:

The regurgitant flow of blood produces a high-pitched diastolic murmur starting after the second heart sound. There is no gap between the second sound and the onset of the murmur. Usually it is best heard along the left sternal edge in the third and fourth interspace. One can detect the murmur easily if the patient is asked to sit up, lean forward and to hold his breath after expiration. If the murmur is also heard over the right sternal border, it indicates that there is dilatation of aortic ring and of ascending aorta.

A concomitant systolic murmur is usually present in aortic incompetence and does not necessarily indicate the presence of co-existing aortic stenosis. The systolic murmur is explained by turbulence in the aorta caused by rapid ejection of a large amount of blood. If the aorta is dilated, a systolic thrill may also be felt.

A low pitched diastolic murmur with or without pre­systolic accentuation may be heard over the apex suggesting a co-existing mitral stenosis. This murmur known as Austin-Flint murmur is produced by vibration of the anterior leaflet as the regurgitant stream impedes full opening of the mitral valve.

Peripheral vascular signs apart from collapsing pulse and capillary pulsation are Traube’s pistol shot sound audible over the femoral arteries and Duroziez double intermittent crural souffle which comprise of a systolic murmur over the femoral artery and diastolic murmur which is audible when pressure is applied distal to the point of auscultation.

The blood pressure is characterised by a wide pulse pressure caused by a low diastolic pressure. In younger patients the Korotkoff’s 4th or 5th sound may be heard falsely down to zero. For accurate estimation of blood pressure, measurement of intra-arterial pressure is required.

In patients with advanced disease arteriolar constriction compensatory to reduced cardiac output may cause rise in diastolic pressure.

Investigations:

Phonocardiogram:

This reveals the presence of aortic diastolic murmurs which starts immediately after the aortic component of second sound. It is diminuendo in shape. A progressive decrease in the duration of the murmur indicates myocardial functional impairment. A diamond-shaped systolic murmur is also noticeable.

Electrocardiogram:

It may remain normal for many years, but ultimately evidence of left ventricular hypertrophy with tall T waves (diastolic overload pattern) is seen.

Chest Radiograph:

Cardiac silhouette is enlarged, caused by left ventricular enlargement. Valvular calcification is less common in aortic stenosis. In presence of left ventricular failure, signs of pulmonary venous congestion will be evident in the lung fields.

Echocardiography:

Is useful non-invasive investigation. It also helps in assessing left ventricular function and in diagnosing Austin Flint murmur.

Cardiac Catheterisation and Cineaortography:

When the contrast medium is injected at about 4 cm. above the aortic valve, regurgitation of dye into the left ventricle can be demonstrated. The degree of reflux may also be estimated. In severe regurgitation there is almost complete opacification of the left ventricular cavity.

Treatment:

Patients with trivial aortic incompetence often remain asymptomatic but they are prone to infective endocarditis and should be protected by appropriate antibiotics before any dental procedure, invasive investigations etc. Trinitrin tablets are helpful in relieving angina. Diuretics can be used as required but over diuresis is dangerous. Valve replacement is the treatment of choice.

Although one would usually like to wait until some symptoms appear, there is little advantage in waiting when the heart size is progressively increasing or the electrocardiogram is deteriorating. Patients presenting with effort syncope and intractable angina should be operated as early as possible. Coronary arteriography can be conveniently carried out during aortography.

Valve replacement:

Either a biological tissue valve or a prosthetic valve is usually used. Mortality from prosthetic valve replacement is less than 10 percent but occurrence of embolism should always be prevented by long-term anticoagulant therapy. The mortality of tissue valve replacement is little higher than replacement by prosthesis.

Disorder # 6. Cardiomyopathy:

(Syn: Myocardiopathy: Myocardial disease)

Introduction:

Heart muscle diseases of unknown aetiology are classed as cardiomyopathy (CMP). The disorder is usually a chronic myocardial disease usually ending in fatality once failure sets in. Acute or subacute myocarditis may also occur.

Aetiological classification varies but cardiac disorders due to coronary heart disease, hypertension, rheumatic heart disease, thyroid disorder, syphilis and congenital heart diseases are excluded from the list of aetiology of CMP. Previously CMP used to be classified into two types — primary and secondary but recently this classification is being revised.

The modern concept is to evaluate the cause whenever possible and call it a specific heart muscle disease. However, in most cases it becomes a guess-work as heart muscle biopsy is not routinely possible. Until more satisfactory classification and better methods of aetiological diagnosis are available, the following classification may be considered useful, at least to explain the ill-understood subject of CMP.

Aetiology:

Possible factors may be follows:

(1) Idiopathic — where no cause can be found, hence this was previously called primary CMP. Familial occurrence is well-known.

(2) Viral — Coxsachie-B virus, influenza, infectious mononucleosis, diphtheria, toxoplasmosis, Chagas disease, etc. may cause myocarditis, recognised during or weeks after the acute illness.

(3) Alcohol, emetine, arsenic, cobalt, ethylene glycol etc. also may be responsible.

(4) Infiltrative disorders: Sarcoidosis, amyloidosis, collagen diseases, gargoylism, glycogen storage disease, haemochromatosis can cause CMP.

(5) Neuromuscular disorders e.g. Friedrich’s ataxia, progressive muscular dystrophy and dystro­phia myotonica may be associated with CMP.

(6) Postpartum CMP occurs usually two to several weeks in post-partum period. Why it occurs is not clear.

(7) Nutritional CMP (Beriberi) due to deficiency of vitamin B₁ (aneurin) is well known.