notes by dr Claudio Italiano
Hypertrophic cardiomyopathy is a disease of the heart muscle that is
characterized by the enlargement of the walls of the heart which begins at the
level of the septum, and then extends to the rest of the chamber of the left
ventricle.
Why does the heart grow bigger?
Because any muscle if subjected to continuous work, develops, especially under strain; for example, an athlete who lifts weights will have muscles in the hypertrophic arms.
Now suppose that the left ventricle during its pumping process encounters a greater resistance to the outflow of the blood and therefore that it strives: this happens for ex. in the patient with arterial hypertension, or in the valvulopathies, in our case, aortic stenosis or in the steno-mitral insufficiency.
In these conditions, before exhausting (remember that a thick wall is oxygenated badly and goes into ischemia and decompensation!) The ventricle, therefore, becomes hypertrophied. Furthermore, the myocardial fibers that must be well organized, instead suffer a disarray, that is a disordered rearrangement with an increase in the fibrous tissue, which replaces the contractile tissue.
We can not talk about hypertrophic cardiomyopathy in the case of athletes who train; some individuals may be carriers of the genetic mutation of this disease, but have a normal echocardiogram and electrocardiogram, not being in this way identifiable with the usual clinical tools. Finally, remember that untreated arterial hypertension, over time can cause hypertrophy of the myocardium and the same applies to those conditions, such as the stenosis of the mitral or aortic valve that in the long run cause the hypertrophy of myocardium.
It can be:
- Concentric, ie it affects the heart chamber at full thickness and is the most
dangerous for cardiovascular events
- Eccentric, ie limited to some portions of the myocardium, for example the tip,
which happens in Japanese patients, or can take an "hourglass" appearance.
The problem is that some parts of the myocardium are subjected to greater wall
pressure and, therefore, at risk of major ischemia and at risk of the onset of
dangerous complications such as ventricular arrhythmias and / or the genesis of
Q waves, expression of wall injury currents.
There is, however, a physiological hypertrophy, which is that of the athlete who trains. These cases are an example of what we could call Hypertrophic Cardiomyopathy without hypertrophy. Finally, there are certain conditions in which the myocardium undergoes a thickening of the wall; they are genetic diseases, of tesaurismosi, that is of accumulation of substances for genetic defect of the metabolism. For example, Fabry's disease, a rare disorder of lipid metabolism characterized by the progressive accumulation of glycolipids, within many tissues. The cause lies in the deficiency of alpha-galactosidase, the enzyme responsible for the catabolism of glycolipids themselves.
It is a hereditary disease linked to the X chromosome. The clinical picture is characterized by skin lesions (angiocheratomas) in the lower part of the trunk, joint pains, renal and cerebrovascular complications (heart attack, stroke). Today an enzyme replacement therapy is available to treat this disease.
Finally, a sign should also be made to amyloidosis, a disease that may be primitive, or secondary to other diseases, characterized by the accumulation of amyloid substance (a protein) in various organs and tissues, pathology that occurs after age 50, and it also affects the heart that shows thickened walls as in hypertrophic cardiomyopathy, even if the increase in thickness is borne by all the walls. The electrocardiogram viceversa can be very useful in distinguishing these two different pathologies.
In forms with obstruction, ie where the upper portion of the septum is involved, with movement of the mitral valve in systole, ie during the contraction of the myocardium in systole, the valve moves forward with a systolic anterior movement called SAM, which creates obstruction blood flow, and generates a sound that does not make the heart sound, but a breath, at the auscultation. Moreover this alteration causes blood regurgitation in the atrium, since the valve is not a continent. The same can happen with the aortic valve, but in this case the ejection deficit can be quantified in 25%.
The subjects, however, may have syncope and fainting, which sometimes depends on ischemic facts of the myocardium to which they achieve dangerous ventricular arrhythmias. On the other hand, in some patients, particularly important symptoms can be explained almost completely by the presence of the obstruction. The obstruction is expressed in millimeters of mercury (mm Hg) and can be measured with non-invasive instruments such as Doppler echocardiography, or with cardiac catheterization with which a direct determination of the pressures is obtained using catheters introduced into the cardiac cavity passing through arteries of the arms or legs.
The term obstruction then indicates the difference in pressure (or pressure gradient) between the left ventricle and the aorta. It must also be said that the heart muscle in hypertrophy is rigid and is released little when the blood enters the ventricles during systole, ie when it should fill with blood, and this creates yet another pump deficit.
It follows that the subject feels "breathless" and dyspnoic (dyspnea). In the most serious cases, and especially in the elderly, ischemic heart disease also appears, and it is responsible for episodes of chest pain and angina, with the risk of arriving at a clear picture such as that of myocardial infarction or sudden death!
In these cases, ischemia occurs with different mechanisms than those of coronary disease: it seems that it depends on small arteries within the heart muscle, with small lumen or that depends on the wall pressure that is increased, resulting in ischemia, that is, reduced blood supply. Unfortunately, in Hypertrophic Cardiomyopathy, the identification of ischemia with diagnostic investigations is difficult and often not reliable; therefore, the precise assessment of ischemia in patients remains a difficult problem.
Neither with the ecg nor with the echocardium is it possible to come to terms with it. Recently a new method has been used, which is myocardial magnetic resonance, which has the purpose of using contrast media such as gadolinium, to clarify whether or not there are ischemic areas or previous necrosis, not identified with classical meiotic. This is obviously a new technique, still in the experimental phase, which seems to give new light to the cardiologist who fails with the current means to diagnose ischemic heart disease.
We start with classic ecg, which to remember the teacher prof. Peppe Oreto,
who at the last congress of the Policlinico di Messina, talks about "new
technique", to signify that the ecg if well performed and well interpreted, can
give invaluable information about the site of lesions and even hypertrophy of
myocardium in the BBS, where other authors remain perplexed. The professor
confirms and explains that it is precisely in hypertrophic heart disease with
BBS, whose branch block (ecg 2) is the consequence of hypertrophy, that the ecg
is used and clarifies the hypertrophic condition, better than an echocardium.
So if the clinic guides us, the track often reveals the presence of a heart
murmur. There are several instrumental examinations that are used to establish
the diagnosis of the disease and assess its severity:
- 12-lead electrocardiogram is the first exam and assesses the presence of
arrhythmias and may identify abnormalities secondary to cardiac hypertrophy.
- Echocardiogram: main examination for the diagnosis and evaluates the extent of
the disease, the presence of obstruction of the outflow tract of the left
ventricle and the function of the heart.
- Holter electrocardiographic monitoring according to Holter, ie track
recordings for 24 hours or more.
- Exercise ecg test used to assess the patient's ability to exercise, and the
response of heart rate and blood pressure during physical exertion.
- Magnetic resonance, in addition to the echocardiogram, provides accurate
information on the structure and function of the heart. Moreover, by injection
of a Gadolinium, it is able to assess the presence of macroscopic areas of
fibrosis.
- Invasive technique of cardiac catheterization, to evaluate possible
regurgitation from the ventricle into the aorta and get an idea of the state
of the coronary and of the stenosis situations of the vessels. Recall that the
coronary vessels are the vessels that supply the heart (cf treatment of the
infarct).
In most cases the disease has a benign course. Some patients may develop symptoms that require pharmacological intervention and, in more severe cases, invasive interventions such as myomectomy or alcoholic ablation of the interventricular septum. For the problem of arrhythmias, an automatic defibrillator may be indicated for preventive purposes. Medical therapy uses the use of cardioselective beta-blockers, calcium antagonists, ace-inhibitors and especially Spartans, such as losartan. The loop diuretics in case of heart failure find particular indication, along with aldosterone blockers.