Diastolic dysfunction in stunned myocardium: a state of abnormal excitation–contraction coupling that is limited by Na+–H+ exchange inhibition

Helical structure of the ventricular myocardium. A narrative review of cardiac mechanics

To date, the ventricular myocardial band is the anatomical-functional model that best explains cardiac mechanics during systolic-diastolic phenomena in the cardiac cycle. The implications of the model fundamentally affect the anatomical interpretation of the ventricular myocardium, giving meaning to the direction that muscle fibers take, turning them into an object of study with potential clinical, imaging, and surgical applications. Re-interpreting the anatomy of the ventricular muscle justifies changes in the physiological interpretation, from its functional focus as a fiber unraveling the mechanical phenomena carried out during systole and diastole. We identify the functioning of the heart from the electrical and hemodynamic point of view, but it is necessary to delve into the mechanics that originate the hemodynamic changes observed flowmetrically, and that manifested during the pathology. In this review, the mechanical phenomena that the myocardium performs in each phase of the cardiac cycle are broken down in detail, emphasizing the physical displacements that each of the muscle segments presents, as well as a vision of their alteration and in which pathologies they are mainly identified. Visually, an anatomical correlation to the echocardiogram is provided, pointing out the direction of the segmental myocardial displacement by the strain velocity vector technique.

Myocardial protection: a forgotten modality

The goals of a cardiac surgical procedure are both technical excellence and complete protection of cardiac function. Cardioplegia is used almost universally to protect the heart and provide a quiet bloodless field for surgical accuracy. Yet, despite the importance of myocardial protection in cardiac surgery, manuscripts or dedicated sessions at major meetings on this subject have become relatively rare, as though contemporary techniques now make them unnecessary. Nevertheless, septal dysfunction and haemodynamic support (inotropes, intra-aortic balloon pump, assist devices) are common in postoperative patients, indicating that myocardial damage following cardiac surgery is still prevalent with current cardioplegic techniques and solutions. This article first describes why cardiac enzymes and septal function are the ideal markers for determining the adequacy of myocardial protection. It also describes the underappreciated consequences of postoperative cardiac enzyme release or septal dysfunction (which currently occurs in 40-80% of patients) from inadequate protection, and how they directly correlate with early and especially late mortality. Finally, it reviews the various myocardial protection techniques available to provide a detailed understanding of the cardioplegic methods that can be utilized to protect the heart. This will allow surgeons to critically assess their current method of protection and, if needed, make necessary changes to provide their patients with optimal protection.

What Is the Heart? Anatomy, Function, Pathophysiology, and Misconceptions

Cardiac dynamics are traditionally linked to a left ventricle, right ventricle, and septum morphology, a topography that differs from the heart's five-century-old anatomic description of containing a helix and circumferential wrap architectural configuration. Torrent Guasp's helical ventricular myocardial band (HVMB) defines this anatomy and its structure, and explains why the heart's six dynamic actions of narrowing, shortening, lengthening, widening, twisting, and uncoiling happen. The described structural findings will raise questions about deductions guiding "accepted cardiac mechanics", and their functional aspects will challenge and overturn them. These suppositions include the LV, RV, and septum description, timing of mitral valve opening, isovolumic relaxation period, reasons for torsion/twisting, untwisting, reasons for longitudinal and circumferential strain, echocardiographic sub segmentation, resynchronization, RV function dynamics, diastolic dysfunction's cause, and unrecognized septum impairment. Torrent Guasp's revolutionary contributions may alter future understanding of the diagnosis and treatment of cardiac disease.

Ventricular structure-function relations in health and disease: part II. Clinical considerations

Normal cardiac function of the left and right ventricles, together with the septum, is related to form/function interactions within the helical ventricular myocardial band. This knowledge is a prerequisite to understanding form/function interactions in diseases and for planning new treatments. Topics discussed include congestive heart failure in dilated hearts of ischaemic, valvar or nonischaemic origin as well as diastolic dysfunction. Similar thinking underlies novel treatments for dyssynchrony in pacing, together with focusing upon varying global left or right ventricular anatomy to correct mitral and tricuspid insufficiency caused by tethering of the leaflets. The septum is the lion of the right ventricle and insight is provided into offsetting septal damage during cardiac surgery, rebuilding its anatomical structure in post-tetralogy pulmonary insufficiency, as well as rectifying its dysfunction by decompression in patients with a left ventricular assist device.

Persistence of systolic and diastolic regional dysfunction after brief episodes of myocardial ischemia evaluated with velocity vector imaging

BACKGROUND

The time course and characteristics of persistent regional dysfunction after ischemia remain unclear. Velocity vector imaging (VVI) allows accurate quantification of regional myocardial function. The aim of this study was to characterize the time course of regional diastolic and systolic abnormality after recovery from different durations of ischemia by VVI.

METHODS

72 rats underwent brief left coronary occlusion (3, 5, 10 and 15 min, respectively) followed by reperfusion for 4-8h. Hemodynamic measurements and VVI were performed at various time points. Regional systolic and diastolic functions were estimated from peak diastolic and systolic circumferential strain rate (SR-d and SR-s) of the left ventricle, respectively.

RESULTS

Both SR-d and SR-s were significantly decreased in the ischemic segment during occlusion compared to non-ischemic segment. With the increase in occlusive time, the duration of reduced SR-d and SR-s after reperfusion was prolonged. Both SR-d and SR-s returned to pre-occlusion values in less than 30 min after reperfusion in the 3 min and 5 min ischemia groups. However, in the 10- and 15-min ischemia groups, SR-d did not fully recovered even at 240 min after reperfusion despite complete recovery of SR-s. The left ventricular hemodynamics during occlusion were significantly changed in all groups and returned to baseline immediately after reperfusion.

CONCLUSION

The persistence of diastolic regional dysfunction is longer than systolic regional dysfunction after a relative longer ischemic event, suggesting that recent myocardial ischemic insult mimicking variant angina may be recognized with the evaluation of regional diastolic function.

Oral calcium supplementation ambulatory blood pressure and relation to changes in intracellular ions and sodium-hydrogen exchange

BACKGROUND

Calcium (Ca2+) supplementation has been shown paradoxically to reduce intracellular Ca2+ and induce vascular relaxation. The aim of the study was to assess 24-h blood pressure (BP) change after Ca2+ supplementation and to investigate its relation to changes in intracellular ions and the activity of the first isoform of sodium-hydrogen exchange (NHE-1) in subjects with hypertension and type 2 diabetes.

METHODS

This parallel, randomized controlled, single-blinded trial, consisted of 31 patients with type 2 diabetes, and hypertension who were allocated to receive 1,500 mg of Ca2+ per day (n = 15) or no treatment (n = 16) for 8 weeks.

RESULTS

In the Ca2+ group a decrease of 1.7 +/- 2.7 mm Hg (mean +/- SE) P = 0.52 for mean 24-h systolic BP (SBP) and 2.1 +/- 1.5 mm Hg, P = 0.19 for mean 24-h diastolic BP (DBP) was recorded. Whereas in the control group an increase of 1.4 +/- 2.7 mm Hg, P = 0.59 for mean 24-h SBP and 1.2 +/- 2.8 mm Hg, P = 0.83 for mean 24-h DBP was observed. Intraplatelet Ca2+ decreased whereas intraplatelet magnesium (Mg2+) and erythrocyte K+ increased in the intervention group. Change in mean 24-h SBP in the pooled group correlated with both change in intraplatelet Ca2+ (r = 0.49, P < 0.05) and NHE-1 activity (r = 0.6, P < 0.001). The contribution of intraplatelet Ca2+ was attenuated when both parameters were entered in a multivariate regression model.

CONCLUSIONS

The present study shows a weak, statistically nonsignificant trend towards association of Ca2+ supplementation on 24-h BP in hypertensive subjects with type 2 diabetes. However, our results indicated an interrelation of [Ca2+]i levels and NHE-1 activity on BP in patients with hypertension and type 2 diabetes.

Left ventricular diastolic dysfunction of the cardiac surgery patient; a point of view for the cardiac surgeon and cardio-anesthesiologist

BACKGROUND

Left ventricular diastolic dysfunction (DD) is defined as the inability of the ventricle to fill to a normal end-diastolic volume, both during exercise as well as at rest, while left atrial pressure does not exceed 12 mm Hg. We examined the concept of left ventricular diastolic dysfunction in a cardiac surgery setting.

MATERIALS AND METHODS

Literature review was carried out in order to identify the overall experience of an important and highly underestimated issue: the unexpected adverse outcome due to ventricular stiffness, following cardiac surgery.

RESULTS

Although diverse group of patients for cardiac surgery could potentially affected from diastolic dysfunction, there are only few studies looking in to the impact of DD on the postoperative outcome; Trans-thoracic echo-cardiography (TTE) is the main stay for the diagnosis of DD. Intraoperative trans-oesophageal (TOE) adds to the management. Subgroups of DD can be defined with prognostic significance.

CONCLUSION

DD with elevated left ventricular end-diastolic pressure can predispose to increased perioperative mortality and morbidity. Furthermore, DD is often associated with systolic dysfunction, left ventricular hypertrophy or indeed pulmonary hypertension. When the diagnosis of DD is made, peri-operative attention to this group of patients becomes mandatory.

Structure and function relationships of the helical ventricular myocardial band

OBJECTIVE

Understanding cardiac function requires knowledge of the architecture responsible for the normal actions of emptying and filling. Newer imaging methods are surveyed to characterize directional (narrowing, shortening, lengthening, and widening) and twisting motions.

METHODS

These movements are defined and then compared with a spectrum of models to introduce a useful "functional anatomy" that explains cardiac spatial and temporal relationships. The sequential nature of normal contraction differs from a synchronous beat.

RESULTS

The prior concept of constriction is replaced by understanding that clockwise and counterclockwise helical motions are necessary to cause the predominant twisting motion. The helical ventricular myocardial band model of Torrent-Guasp fulfills the architectural structure to define normal function. Expansion of information from this model allows novel understanding of mechanisms that explains why a component of ventricular suction involves a systolic event, clarifies septum function, determines diastolic dysfunction, introduces new treatments, shows how knowledge of the helical structure influences understanding of atrioventricular and biventricular pacing, and creates novel methods for introducing septal pacing stimuli.

CONCLUSION

Further testing of these spatial anatomic concepts is needed to create a more accurate understanding of the architectural mechanisms that underlie cardiac dynamics to address future problems in unhealthy hearts.

Barium-enhanced imaging of the coronary vasculature of the porcine myocardium: empirical investigation into the theory of the ventricular myocardial band

OBJECTIVE

The ventricular myocardium is thought to exist as a single continuous muscle band that extends from the pulmonary artery to the aorta, wrapped into a double helical coil Torrent-Guasp's theory of the ventricular myocardial band (VMB). The purpose of this study was to examine the coronary blood supply to the VMB and to evaluate the effect of coronary blood systems on structure-function relations in the myocardium.

METHODS

VMBs of nine swine hearts were unwrapped after postmortem barium coronary angiography. Unwrapped VMBs underwent radiography, and vascular images of barium remaining in the VMBs were evaluated.

RESULTS

We were able to achieve a single longitudinal and stretched myocardial band in all nine porcine hearts. The corresponding regions supplied by each coronary artery were clearly distinguishable in the VMBs. The right segment of the basal loop was supplied by the right coronary artery. The left segment of the basal loop was supplied by the left circumflex artery. Most of the descending segment of the apical loop was supplied by the left anterior descending artery, with an inferior portion supplied by the right coronary artery. Most of the ascending segment of the apical loop was supplied by the left anterior descending artery, with a posterior portion supplied by the left circumflex artery.

CONCLUSION

Understanding the trinity of structure, function, and coronary blood supply from the viewpoint of the VMB should facilitate development of more effective surgical treatment for severe ischemic heart disease.