Ventricular wall motion analysis and "The law of the Heart" (Frank-Starling law)
Cardiac activity can be correctly described using the laws of dynamic physics.
VENTRICULAR WALL MOTION ANALYSIS AND THE "LAW OF THE HEART"
(Frank-Starling law)
G. Bozzi
In the late '80s, the opening of the new Cath. Lab. Sacco Hospital in Milan led to an organizational effort that has also affected the reporting system of examinations and their storage. The availability of reasonably priced computer prompted me to the use of these machines and the preparation of programs suitable to our needs. Things went well for many problems (classical calculations: flow, valvular areas, description of anatomy and coronary artery disease), but a seemingly insurmountable difficulty appeared with trying to get an objective reading of the left cine-ventriculography (CVG ). The literature of the time provided different calculation models (Fig. 1), but none of these produced diagnoses like those of experts angiographers.
Fig. 1. Five methods of wall motion analysis proposed in the '80. A: shortening of segments orthogonal to long axis[1]. B: shortening of radial segments starting from a "center of contraction[2]. C: Reduction of areas orthogonal to long axis[3]. D: endocardial land-marks. E: centerline [4].
All methods subjected to tests have shown three serious flaws:
1) large standard deviation (SD) of calculated points
2) contraction curve irregularity/asymmetry
3) reduction of contraction efficacy at the apex
whereas an ideal contraction curve should:
1) have low SD
2) be symmetrical and regular
3) show maximal contraction efficacy at the apex.
For it seems unnecessary to store the contraction curves without diagnostic capability, I decided to organize of computer tests by comparing two modes of calculation at a time of a normal case series, with the objective of identifying in each test the most effective calculation. Figure 2 shows an example of this search mode. Having established in previous tests that the best result was obtained with the calculation of the reduction of areas orthogonal to the longitudinal axis, the question of this test was to determine which areas to attribute the longitudinal axis shortening.
Fig. 2. Example of an algorithmic test: in A long axis shortening was attributed to basal areas 1, 2, 19, 29. In B to all areas. In C: to apical areas 9, 10, 11, 12. [6]
Given the trend of the curves, it is not difficult to conclude that the correct choice is B. This test, which at first glance would seem superfluous given the obviousness of the answer, revealed an unexpected problem: the apical sectors show a significant increase in standard deviations compared to other sectors (10-12% to 50%), indicating a problem of the evaluation of the apex contraction. In particular, it was not clear the reason why in some cases the tip appeared at other hypokinetic and hyperkinetic while having the silhouettes similar morphologies. This defect has suggested the suspicion of an upstream failure of the calculations, so out of control. The thought went to the concept of cardiac contraction formulated over a century ago and known as volume/pressure diagram or the Frank-Starling law of the heart (fig. 3). I wondered why such an elegant description and success had not found any application in clinical practice. Meditating around this consideration, I realized that volume and pressure are variables of static physics (gas law: PV = nRT), while the heart accelerates two masses of blood, so it is subject to the laws of motion (inertia, conservation, and action-reaction).
Fig. 3. Volume/pressure relationship (Frank-Starling law). a-b isovolumic contraction. b-c ejection. c-d isovolumic relaxation. d-a ventricular filling.
In particular, the second law of motion (F = ma) tells us that each blood ejection, a heart at rest generates a force of about 1.37 N (note 1). In other words, the chest should receive a shock at each cardiac contraction, which not only does not occur, but we do not perceive at all the heart activity. The only reasonable explanation is that the heart works in a balanced way. It 'was then formulated the hypothesis that for the third principle of dynamics (action-reaction) the heart at each systole moves the side opposite to that of the ejected blood, and the dynamic balance is due to equality between lowering of the heart mass and shortening of the cavities. We subjected this hypothesis to an algorithmic test for the left ventricle; the shortening observed in angiographic projection RAO is the actual amount of shortening of the cavities and the effacement of the walls at the apex. Subtraction can then calculate the extent of this affixing. The test produced the results in Figure 4 and convinced me of the correctness of the hypothesis. A few years after the formulation of this hypothesis and its computerized analysis, a case of primary angioplasty randomly gave me the angiographic demonstration of its correctness (see the fourth movie in the series).
Fig. 4. Graphic representation of the Klinger method and mean contraction curve obtained from 14 normal cases. AD: aortic plane displacement. AMd: distance between the proximal end of the longitudinal axis (LA) and the mitral fornix or (in this case) the boundary between the outflow tract and the anterobasal wall. AMs: the systolic equivalent of AMd, and is obtained by calculation. edLAc: end-diastolic LA calculated. edLAm: end-diastolic LA measured. esLAc: end-systolic LA calculated. esLAm: end-systolic LA measured. SCA: systolic concealed apex [7].
I declare my satisfaction with the result and the expectation of the emergence of Klinger contraction curves on medical textbooks (which, of course, did not occur). He also hits the number of articles on this topic published by renowned medical journals over many years without anyone ever asked why the clinical futility of the proposed methods, and/or have tried a justification to the presence of equal defects in different calculation methods. Yet these are two signs of a fundamental error, probably upstream of the calculations: typical example of a logical leap containing an error.
Until the moment when I asked myself these questions, the articles published by magazines such as Computers in Cardiology or Circulation, represented in my imagination medical what the gospel is in religion: unquestioned truth. I was now obliged to take note that, at least on this subject, all had fantasies published out of control, in accordance with the saying: "... in the junk computer comes in, garbage out."
The next question seemed to me worrying: if cardiologists and leading medical journals auditors (which would seem logical to assume intelligent and prepared) published for years blatantly erroneous assumptions and calculations on a topic verifiable logical-mathematical terms, what happens when we reason on topics that can't be subjected to any kind of verification? I refer to philosophy and religion. This question has caused me a sense of insecurity, because I asked on what basis laid the foundations of my life choices. I therefore decided to address the problem and I did it in three writings which I have published on Amazon.
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Note 1. Ejected mass 0.088 kg each ventricle; max velocity in the aorta 1.10 m/sec; max speed pulmonary artery 0.90 m/sec; ejection time 250 ms. Let us suppose the accelerations are constant, and the blood reaches these speeds at half the ejection time. The sum of the vectors must be made taking account of a divergence of approximately 10°. Newton (N) = force necessary to impart to the mass of 1 kg acceleration of 1 m/sec2.
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