WITHDRAWN: Influences of Perfusion Pressure and Pulsatile Flow on Cerebral Flow Reserve and Oxygenation in the Isolated Perfused Swine Brain under Normothermia.

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Surgical restoration of the postinfarction dilated ventricle.

Surgical restoration of the failing heart is related to rebuilding cardiac architecture and linked to: (a) understanding that the structure of the failing dilated heart involves changing the normal elliptic shape toward a dilated spherical form; (b) recognizing the anatomic fiber orientation framework and its functional implications; (c) establishing imaging measurement guidelines to determine indications for surgical intervention that focus upon volume and remote muscle evaluation rather than ejection fraction; and (d) summarizing left ventricular restoration results whereby rebuilding normal elliptic configuration improves function, reduces ventricular arrhythmias, alleviates mechanical dyssynchrony, and causes progressive improvement that extends long-term prognosis.

A new look at diastole.

The isovolumic period following systolic ejection is associated with untwisting of the apex that follows systolic torsion of the left ventricle, with simultaneous generation of negative pressures in the left ventricle. Previous studies have described this period as isovolumic relaxation, and have regarded the untwisting as entirely caused by restoring elastic forces. However, evidence from several sources indicates that some ventricular muscle is still contracting during this period, and that this muscle is subepicardial muscle or the ascending spiral segment of the ventricular myocardial band that extends from the apex up along the left ventricular epicardium and the right ventricular side of the septum to the root of the aorta. It is possible that diastolic dysfunction is due to defective incoordination of muscle contraction between the ascending and descending segments of this band rather than to defective passive restoring forces.

Mitral regurgitation: anatomy is destiny.

Mitral regurgitation (MR) occurs when any of the valve and ventricular mitral apparatus components are disturbed. As MR progresses, left ventricular remodelling occurs, ultimately causing heart failure when the enlarging left ventricle (LV) loses its conical shape and becomes globular. Heart failure and lethal ventricular arrhythmias may develop if the left ventricular end-systolic volume index exceeds 55 ml/m2. These adverse changes persist despite satisfactory correction of the annular component of MR. Our goal was to describe this process and summarize evolving interventions that reduce the volume of the left ventricle and rebuild its elliptical shape. This 'valve/ventricle' approach addresses the spherical ventricular culprit and offsets the limits of treating MR by correcting only its annular component.

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.

An experimental and clinical evaluation of a novel central venous catheter with integrated oximetry for pediatric patients undergoing cardiac surgery.

BACKGROUND: Central venous oxygen saturation (ScvO2) accurately reflects cardiocirculatory function, but is not always feasible in pediatric patients. Using an experimental and clinical approach, we determined the accuracy of a novel pediatric central venous catheter with integrated fiberoptic oximetry, correlated ScvO2 to periprocedural vital variables, and tested its feasibility in pediatric cardiac surgery patients. METHODS: In five anesthetized pigs, hemodynamics (cardiac index [CI], heart rate; mean arterial blood [MAP]; mean pulmonary artery [MPAP], central venous pressure [CVP]), fiberoptic ScvO2 (ScvO2-cath), and blood gas oximetry (ScvO2-blood) were measured during stable baseline conditions, preload reduction (caval occlusion), and dopamine infusion (5 mcg x kg(-1) x min(-1)). In 16 pediatric patients undergoing cardiac surgery (median age 8.4 mo; weight 8.0 kg), central venous oximetry catheters were placed percutaneously, and ScvO2-cath and hemodynamics recorded at several time-points during and until 24 h after surgery. Oximetry and hemodynamic data were compared by correlation (Pr) and the Bland-Altman analysis. RESULTS: There were no catheter-related complications. ScvO2-cath and ScvO2-blood measurements correlated significantly (P < 0.001) in both the experimental (Pr = 0.96) and clinical protocol (Pr = 0.94). A similar bias and precision over all time-points was detected in both protocols (Exp-bias: +0.03% +/- 4.11%; Clinical-bias: -0.03% +/- 4.41%). ScvO2-cath correlated (P < 0.001) with CI (Pr = 0.87), MAP (Pr = 0.59), MPAP (Pr = 0.44), and CVP (Pr = 0.38) and estimated CI better than MAP (Pr = 0.61), MPAP (Pr = 0.38), CVP (Pr = 0.35), or heart rate (Pr = 0.25). CONCLUSION: Integrated central venous oximetry catheters provide accurate continuous ScvO2 monitoring in pediatric patients undergoing cardiac surgery. ScvO2 fiberoptic oximetry correlates better with changes in CI as compared to routine hemodynamic variables.

Pathophysiologic implications of the helical ventricular myocardial band: considerations for right ventricular restoration.

This chapter describes the structure/function relationships of the right ventricle (RV), and shows how the geometry of the helical ventricular myocardial band model defines spatial geometry of the free wall and septum that underlie dynamic action. Myocardial fiber orientation is the keynote to performance in health and disease. The transverse geometry of the RV free wall allows constriction (bellows-type motion), whereas oblique septal fiber orientation and midline septal position is essential for ventricular twisting, the vital mechanism for RV ejection against increased pulmonary vascular resistance. Therefore, the septum is considered "the lion or motor of RV performance." Distortion of such normal structure/function relationships underlies the pathophysiologic mechanisms of RV failure. Operative methods that restore normal myocardial fiber orientation are described to outline evolving surgical techniques for the surgical treatment of RV failure.

Sudden cardiac death: directing the scope of resuscitation towards the heart and brain.

BACKGROUND: The fundamental goal of cardiopulmonary resuscitation (CPR) is recovery of the heart and the brain. This is best achieved by (1) immediate CPR for coronary and cerebral perfusion, (2) correction of the cause of cardiac arrest, and (3) controlled cardioplegic cardiac reperfusion. Failure of such an integrated therapy may cause permanent brain damage despite cardiac resuscitation. METHODS: This strategy was applied at four centers to 34 sudden cardiac death patients (a) after acute myocardial infarction (n = 20), (b) "intraoperatively" following successful discontinuation of cardiopulmonary bypass (n = 4), and (c) "postoperatively" in the surgical ICU (n = 10). In each witnessed arrest the patient failed to respond to conventional CPR with ACLS interventions, including defibrillation. The cardiac arrest interval was 72 +/- 43 min (20-150 min). Compression and drugs maintained a BP > 60 mmHg to avoid cerebral hypoperfusion. Operating room (OR) transfer was delayed until the blood pressure was monitored. In four patients femoral bypass maintained perfusion while an angiographic diagnosis was made. RESULTS: Management principles included no repeat defibrillation attempts after 10 min of unsuccessful CPR, catheter-monitored peak BP > 60 mmHg during diagnosis and transit to the operating room, left ventricular venting during cardiopulmonary bypass and 20 min global and graft substrate enriched blood cardioplegic reperfusion. Survival was 79.4% with two neurological complications (5.8%). CONCLUSIONS: Recovery without adverse neurological outcomes is possible in a large number of cardiac arrest victims following prolonged manual CPR. Therapy is directed toward maintaining a monitored peak BP above 60 mmHg, determining the nature of the cardiac cause, and correcting it with controlled reperfusion to preserve function.

Form versus disease: optimizing geometry during ventricular restoration.

OBJECTIVE: Dilated cardiomyopathy from many causes results in a change in ventricular geometry, whereby the elliptical chamber becomes more spherical. This may be the unifying geometric concept of heart failure, with similar alteration of spatial configuration in non-ischemic diffuse myocyte disease, ischemic cardiomyopathy with and without scar, and in valvular heart disease. METHODS: This change in architecture alters fiber direction and diminishes function, and has been related to alteration of the apical loop of the helical ventricular myocardial band model of cardiac shape. The underlying concept of rebuilding the ventricle by ventricular restoration is suggested to be reconstruction of form, rather than focusing on only the underlying disease. RESULTS: Examples are shown where the Surgical Anterior Ventricular Exclusion (SAVE) or Pacopexy procedure has been successfully applied to each of the above-mentioned diseases, and is suggested for dilated valvular cardiomyopathy. The interaction between rebuilding form and how this procedure restores more normal fiber orientation is discussed, and the possibility of a macroscopic/microscopic marriage between surgically altering the cardiac scaffold by restoration (macro) and cell biology to improve function in a new helical shape is suggested. CONCLUSIONS: The implication of these observations is that the surgical objective should become rebuilding ventricular form, rather than restricting restoration procedures to only addressing the disease.

The ventricular septum: the lion of right ventricular function, and its impact on right ventricular restoration.

OBJECTIVE: To evaluate the structure-function relationships of the right ventricle (RV) and septum and determine if the helical ventricular band model would define fiber orientation for maximal force response. Implications were made for right ventricular function. METHODS: The right ventricular free wall and biventricular septum were studied by inserting sonomicrometer crystals at different angulations to determine the maximum response of fiber shortening. These reactions were compared to the lateral left ventricular (LV) wall and further tested by use of positive and negative inotropic drug infusions. RESULTS: The maximum contraction of the free wall was achieved by placing crystals in the transverse orientation angulations, whereas oblique orientation allowed the maximal septal response. Fiber orientation angulation was the same for the LV free wall and septum. These angulations correlate with the MRI-related twisting actions of septal motion needed for ejection and suction for rapid filling. These findings have important impact, because they imply that the septum is 'lion of right ventricular function,' since septal twisting is essential when pulmonary vascular resistance is increased. The incidence of postoperative right heart failure due to septal dyssyncrony, with loss of septal twisting action from inadequate myocardial protection, is explored relative to RV free wall and septum function. Furthermore, early studies of right ventricular restoration in patients with RV dysplasia and RV failure after chronic pulmonary insufficiency following repair of Tetralogy of Fallot are described, with predominant attention directed toward rebuilding normal septal architecture and function. CONCLUSIONS: This experimental and clinical overview indicates that the septum is 'the lion of right ventricular function,' and implies that the use of this knowledge can become an important guideline for planning novel surgical geometric interventions after RV failure.

Use of cardiac magnetic resonance imaging in surgical ventricular restoration.

OBJECTIVE: Surgical ventricular restoration (SVR) is a promising modality for treatment of heart failure due to left ventricular systolic dysfunction, particularly that due to ischemic heart disease. The role of MRI in improving diagnosis, operative planning, and follow-up is reviewed to analyze how one examination may define a spectrum of important considerations. METHODS: Proper patient selection and optimal surgical planning relies on accurate assessment of measures of ventricular volume, function, and viability, and of the mechanics of the mitral valve apparatus. A complete preoperative imaging evaluation includes assessment of the left ventricular volume (both systolic and diastolic), regional and global systolic function, viability of the target area for surgical exclusion and of the remote myocardium, determination of the adequacy of the remote myocardium remaining after proposed SVR to support circulatory function, and of the mitral annular dilatation and inter papillary muscle spacing, factors which contribute to functional mitral regurgitation. RESULTS: Cardiac magnetic resonance imaging (MRI) allows a complete evaluation of these quantities: the ventricular systolic and diastolic volumes (and hence ejection fraction) are easily assessed reproducibly and accurately; the regional wall motion of the asynergic area and the remote myocardium can be measured by several quantitative means, including with myocardial tagging, and the presence or absence of nonviable, irreversible scar can be detected with gadolinium-based interstitial contrast agents. Furthermore, an accurate measurement of the mitral annular dimensions and the papillary muscle spacing can be easily performed using cardiac MRI, allowing planning of effective therapy for mitral regurgitation. CONCLUSIONS: The entire imaging study can be performed in less than 1h, making cardiac MRI a truly useful and comprehensive tool in planning SVR, and for subsequently evaluating results.

Cardiac motion and fiber shortening: the whole and its parts.

Radionuclide ventriculography findings in 24 subjects show that the ventricular blood pool motion goes from base to apex, a finding that contradicts the expectation that an apex to base relationship should exist, because excitation proceeds from apex to base. This discrepancy reflects a difference between motion caused by whole heart transmural action, and regional activity that does not require global movement. Confirmation of the radionuclide ventriculography findings was made from sonomicrometer crystals, echocardiography, and MRI that demonstrated early basal motion. During excitation, only the endocardial muscle is stimulated by the electrical impulse, but transmural motion that is needed for the endocardial motion that is detected by radionuclide ventriculography. Differences between the isometric and ejection phases are described, and there is discussion of how these findings relate to the myocardial band. The reality of twisting and downward motion of the heart observed during ejection only happens following transmural activation, a motion that exists far beyond the QRS electrical signal on the ECG.

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

OBJECTIVE: The systolic and diastolic effects of myocardial stunning were studied to evaluate the contributions of the endocardial and epicardial segments of the ventricular myocardial band, and determine if preconditioning by Na+-H+ exchange (NHE) inhibition effected post-stunning dysfunction. METHODS: Thirteen Yorkshire-Duroc pigs (27.3-38.2 kg) underwent 15 min of mid-LAD clamping. Seven had no protective measures and six were pretreated with IV Cariporide 5 mg/kg 15 min before ischemia. Sonomicrometer crystals evaluated systolic dysfunction (impaired regional shortening) and diastolic dysfunction (contraction extending into early diastole). RESULTS: Before ischemia, contraction started first on the endocardial side followed 82+/-23 ms later by the subepicardium. Endocardial shortening stopped first, coinciding with negative dP/dt onset, while epicardial shortening phase persisted for 92+/-33 ms more during occurrence of rapid LVP descent and development of peak negative dP/dt. Ischemia produced paradoxical bulging of both segments. Sixty minutes after ischemia systolic segment shortening recovered 36+/-24% of baseline values without pretreatment, compared to 75.8+/-15% with Cariporide (p<0.05). Global ejection force (maximum dP/dt) fell 32+/-20% in the unprotected group, but was maintained by Cariporide pretreatment. Diastolic dysfunction always showed continued endocardial contraction into early diastole (occupying 38+/-16% of diastole in untreated hearts), whereas Cariporide treatment reduced this dysfunction to 5+/-10% (p<0.05). Persistent diastolic dysfunction raised left ventricle end diastolic pressure (LVEDP) 4 mmHg in untreated hearts, whereas Cariporide returned LVEDP to normal. Less elevation of creatine kinase MB (CK-MB) and conjugated dienes followed Cariporide pretreatment. CONCLUSIONS: Temporary LAD ischemia alters the normal sequential pattern of contraction responsible for ejection and suction by (a) reducing systolic contractile force, and (b) prolonging endocardial contraction into early diastole to disrupt the normal endocardial-epicardial sequence responsible for ventricular suction. NHE inhibition before ischemia limits postischemic systolic and diastolic dysfunction by re-establishing the expected shortening sequences within the ventricular myocardial band model.

The septal motor of biventricular function.

This paper describes the anatomic spiral arrangement of the cardiac interventricular septum that results in a twisting action that contributes to the forceful ejection of blood from both ventricles during systole. Right ventricular (RV) dysfunction seen in various clinical settings is discussed with reference to the septum and its mechanism of function. The role of the septum in the interdependence of ventricular function is described. The structure/function relationships of the septum are related to maintenance of its oblique fiber orientation and midline configuration; disruption of this spatial relationship is the lynchpin of the concept that 'left heart failure begets right heart failure.' The importance of recognizing how alterations in septal anatomy affect biventricular performance is related to improved understanding of the clinical manifestations of septal dysfunction, designing a management scheme, and determining how to prevent septal injury.

Structure/function interface with sequential shortening of basal and apical components of the myocardial band.

OBJECTIVE: To study the sequential shortening of Torrent-Guasp's 'rope-heart model' of the muscular band, and analyze the structure-function relationship of basal loop wrapping the outer right and left ventricles, around the inner helical apical loop containing reciprocal descending and ascending spiral segments. METHODS: In 24 pigs (27-82 kg), temporal shortening by sonomicrometer crystals was recorded. The ECG evaluated rhythm, and Millar pressure transducers measured intraventricular pressure and dP/dt. RESULTS: The predominant shortening sequence proceeded from right to left in basal loop, then down the descending and up the ascending apical loop segments. In muscle surrounded by the basal loop, epicardial muscle predominantly shortened before endocardial muscle. Crystal location defined underlying contractile trajectory; transverse in basal versus oblique in apical loop, subendocardial in descending and subepicardial in ascending segments. Mean shortening fraction average 18+/-3%, with endocardial exceeding epicardial shortening by 5+/-1%. Ascending segment crystal displacement followed descending shortening by 82+/-23 ms, and finished 92+/-33 ms after descending shortening stops, causing active systolic shortening to suction venous return; isovolumetric relaxation was absent. CONCLUSIONS: Shortening sequence followed the rope-like myocardial band model to contradict traditional thinking. Epicardial muscle shortened before endocardial papillary muscle despite early endocardial activation, and suction filling follows active systolic unopposed ascending segment shortening during the 'isovolumetric relaxation' phase.

Active myocyte shortening during the 'isovolumetric relaxation' phase of diastole is responsible for ventricular suction; 'systolic ventricular filling'.

OBJECTIVE: To study the 'isovolumetric relaxation' phase of rapid ventricular filling by analysis of the shortening of cardiac muscle in the endocardial and epicardial segments of the left ventricle in the dual helical model of the ventricular band, described by Torrent-Guasp. METHODS: In 10 pigs (27-82 kg), temporal shortening by sonomicrometer crystals was recorded while recording ECG, and measuring intraventricular pressure and dP/dt with Millar pressure transducers. RESULTS: The following sequence was observed; shortening began in descending or endocardial segment, and 82+/-23 ms later it was initiated in the epicardial or ascending segment of the band. The descending segment stops shortening during the rapid filling phase of fast descent of ventricular pressure, but the ascending segment shortening continues for 92+/-33 ms, so that active shortening continues during the period of isovolumetric relaxation. During the rapid filling phase, dopamine decreased the interval between completion of endocardial and termination of epicardial contraction from 92+/-20 to 33+/-8 ms. Conversely propranolol delayed the start of epicardial shortening from 82+/-23 to 121+/-20 ms, and prolonged the duration of endocardial contraction, causing a closer (21+/-5 ms vs 92+/-20 ms) interval between termination of contraction of endocardial and epicardial fibers. The resultant slope of the rapid descent of the left ventricular pressure curve became prolonged. CONCLUSIONS: These time sequences show that ongoing unopposed ascending segment shortening occurs during the phase of rapid fall of ventricular pressure. These active shortening phases respond to positive and negative inotropic stimulation, and indicate the classic concept of 'isovolumetric relaxation', IVR, must be reconsidered, and the new term 'isovolumetric contraction', IVC, or systolic ventricular filing may be used.

Septal anterior ventricular exclusion operation (Pacopexy) for ischemic dilated cardiomyopathy: treat form not disease.

OBJECTIVE: Restoration of left ventricle size and shape is an effective surgical procedure in patients with dilated cardiomyopathy. This report defines early and intermediate results following the reshaping of the left ventricle from spherical to ellipsoid configuration in patients with ischemic cardiomyopathy, employing a technique for LV restoration (LVR) that uses form rather than disease as the endpoint for oblique patch placement. METHODS: Between 1998 and 2004, a cohort of 83 patients with dilated ischemic cardiomyopathy underwent an operation to reshape the left ventricle. In 54 patients the Dor procedure was done, and 29 underwent the septal anterior ventricular exclusion (SAVE) procedure to emphasize the elliptical shape, whereby patch placement followed an oblique trajectory between the LV apex and septum below the aortic valve. Ventricular form, rather than the disease scar marked the suture placement site endpoint to create an ellipse. The mean age was 58+/-27, but SAVE patients had larger end systolic volume index (135+/-38 vs 95+/-25). Overall preoperative NYHA functional class III was in 69% and IV in 31 patients, but more SAVE patients were in class IV (38% vs 28%). The procedures were elective in 72 and emergent in 11, with similar entry criteria for each procedure. RESULTS: In combination with LVR operation, mitral surgery was performed in 49/83 and tricuspid annuloplasty in 23/83 patients, but these procedures were more common after SAVE (59% vs 44% and 45% vs 19%, respectively), because of larger LV volumes in SAVE patients; 2.8+/-1.3 coronary artery bypass grafts were used. Perioperative use of IABP or LVAD was 15 and 1, respectively in 83 patients. Hospital death was in 1/11 or 9% after emergent operations and 3/72 or 4% in elective procedures, with no difference between groups. After discharge from the hospital, NYHA class improved to class I or II in 57 patients, class III/IV in 14 patients, with 10 late deaths. The 5-year survival rate after the elective operation was 80.3% in SAVE and with elective operation and 77.4% in the Dor procedure. CONCLUSION: The SAVE or Pacopexy technique is easy to reshape the dilated left ventricle from spherical to ellipsoid form after the LVR, and the resultant improved configuration may contribute to the overall results for patients with ischemic dilated cardiomyopathy.

'The electrical spiral of the heart': its role in the helical continuum. The hypothesis of the anisotropic conducting matrix.

The study of the dissemination of the electrical impulse throughout the ventricular myocardium, which gave rise to the current theories, was carried out without taking into consideration the complex architecture of the cardiac muscle elucidated by more recent researchers. We propose a novel hypothesis based on the special macroscopic structure of the heart, the anisotropic electrical and mechanical behavior of the myocardium, the characteristics of the intercellular matrix and its very special collagen scaffolding, chemical composition, and biochemistry. The unique properties of the intercellular matrix would make it especially suited to function, in conjunction with the specialized conducting system (His-Purkinje system) as an efficient anisotropic conductor for the spread of electrical activation in the heart in order to allow an optimal sequence of excitation-contraction coupling that results in the coordination of effective myocardial contraction in birds and mammals of the most varied known heart rates. An analysis of certain clinical conditions that raise questions regarding current hypothesis and a review of novel techniques for recording transmembrane and extracellular potentials, which will provide a much firmer basis for the study of cardiac activation and the influence of myofiber architecture and which will allow in depth testing of hypotheses are presented.