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PubMed1989

Systolic and diastolic interaction in the assessment of left ventricular function following surgical cardioplegia.

Using regionally implanted sonomicrometry crystals, we have evaluated a new index of regional function (normalised systolic shortening [NSS]) which integrates the systolic and diastolic properties of the left ventricle. Eight dogs (group I) were subjected to standard cardiopulmonary bypass and 45 min of hypothermic (10 degrees C), hyperkalaemic (25 mEq) crystalloid cardioplegia. Seven dogs (group II) underwent occlusion of the left anterior descending (LAD) coronary artery 5 min prior to initiation of cardiac arrest. The occlusion was released after 20 min, before the second cardioplegia infusion. Sarnoff left ventricular (LV) function curves were performed pre-arrest and 20, 40 and 60 min after removal of the cross-clamp. Regional assessment of myocardial function showed 55% +/- 3%, 70% +/- 3% and 70% +/- 5% recovery in the LAD region and 52% +/- 2%, 83% +/- 3% and 88% +/- 4% recovery in the circumflex (Cx) region of group I. In group II the LAD region recovered 27% +/- 1%, 31% +/- 3% and 38% +/- 3% and the Cx region showed 61% +/- 3%, 55% +/- 1% and 65% +/- 5% recovery. Comparison of the new index of ventricular function to standard indices of regional and global function demonstrate that the latter underestimate the degree of myocardial dysfunction after cardioplegic arrest, particularly in situations of acute regional myocardial ischaemia and uneven myocardial protection. The utilization of this index should provide a better standard for the more accurate assessment of interventions designed to decrease myocardial injury during cardioplegic arrest.

Animals↗
PubMed1975

The evaluation of left ventricular function in man. A comparison of methods.

Comparisons of the sensitivities of parameters for assessing left ventricular performance in man were made in 38 patients. The parameters compared were the ejection fraction, ventriculographic contraction patterns, the left ventricular end-diastolic pressure, and the contractile indices including the contractile element velocity at 10 mm Hg (Vce 10) and maximal contractile element velocity (Vmax). The contractile indices were obtained by catheter tip manometry, utilizing developed pressure (DP) to calculate the velocity of contractile element shortening (Vce) from the formula: dp/dt divided by 32 DP. Vce 10 was measured directly and Vmax was derived by linear manual extrapolation of the pressure-velocity plot to 0 mm Hg. Vmax values derived from linear manual extrapolation were compared with values obtained by computer least squares fitting of the Vce and developed pressure data points to single and double exponential equations. The Vce and developed pressure data points fit the single exponential equation better than the double exponential equation but the use of either equation resulted in slightly higher values for Vmax than obtained with linear manual extrapolation. The effect of heart rate on myocardial contractility was eliminated by making comparisons at both a basal and atrial paced rate of 100. Utilizing all methods, 24 patients were identified to have ventricular dysfunction. The contractile indices were significantly less sensitive than any other parameter (P smaller than 0.05) and identified seven patients while the left ventricular end-diastolic pressure, ejection fraction, and presence of asynergy identified 15, 15, and 12 patients, respectively. The use of a common atrial paced rate of 100 did not increase the sensitivity of the contractile indices. Since there was only partial overlapping between parameters in the identification of left ventricular dysfunction, the combination of different parameters was more sensitive than any single parameter alone. It is concluded that several methods are required to identify all patients with left ventricular dysfunction and that the contractile indices are the least sensitive indicator of left ventricular dysfunction.

Blood Pressure Determination↗
PubMed1990

[The function of beta receptors in chronic left ventricular insufficiency].

Hyperactivity of the noradrenergic sympathetic system is one of the essential "compensatory"mechanisms in chronic left ventricular failure. The ensuing stimulation of myocardial beta-adrenergic receptors results in an increase of heart rate and contractility which, to some extent, counterbalances the alteration of left ventricular function, but rapidly reaches its limits: the excessive shortening of diastoles and, mostly, the increase of myocardial oxygen demand neutralize the beneficial haemodynamic effect of beta-adrenergic stimulation, especially when ischaemia is the cause of the heart failure; the chronic exposure of adrenergic receptors to noradrenaline in high concentrations leads to desensitization, to a "down regulation" which primarily affects the beta 1 receptors and spares, at least partly, the myocardial beta 2 receptors which seem to play a quantitatively important inotropic role, particularly in chronic heart failure. These new data on the physiology of the cardiac noradrenergic system have major therapeutic consequences: in practice, the positively inotropic beta-stimulants can only be used for a short period in acute episodes of heart failure; - the use of beta-blockers in low doses is now considered in the treatment of some forms of heart failure; the mechanism of their therapeutic action remains controverted, and their long-term effectiveness in a large patient population is under study; - a new pharmacological class, beta-adrenoceptor partial agonists, seems to give satisfactory clinical and haemodynamic results in mode-rate heart failure, A wider clinical evaluation is needed to determine the therapeutic role of theses new pharmacodynamic agents.

Adrenergic beta-Antagonists↗
PubMed1998

[Doppler tissue imaging of pre-ejection left ventricular wall dynamics in normal subjects].

Pre-ejectional left ventricular wall motion has been demonstrated clinically by angiography. Intramyocardial wall velocities generated by cardiac contraction may be measured by Doppler tissue imaging. The aim of this study was to detect pre-ejectional wall motion and to analyse its sequencer. A long axis M Mode with simultaneous septal and posterior wall imaging was performed in 11 normal subjects (age 37 +/- 15 years) with velocity analysis between the electrocardiographic Q wave and the onset of ejection by digitised analysis between the electrocardiographic Q wave and the onset of ejection by digitised images with automatic velocity extraction (3.8 ms) along a horizontal subendocardial line. The total duration of the pre-ejectional periods in conventional and Doppler tissue imaging are compared. Oscillatory velocimetric appearances with alternate colours of adjacent bands in each wall and a mirror image between walls was observed. The mean and peak velocities of the first four bands were significantly different between the walls (p < 0.001) as were the absolute values between bands 2 (p < 0.02) and 3 (p < 0.006). The duration of band 2, related to motion mainly towards the center of the ventricular chamber exceeded that of the adjacent bands (septum p < 0.02, posterior wall p < 0.001). The correlation coefficient for total duration of the pre-ejectional period between Doppler tissue imaging and conventional Doppler was 0.83, p < 0.05 for the interventricular septum and 0.76, p < 0.04 for the posterior was. The authors conclude that regional pre-ejectional wall motion can be recorded. During isovolumic contraction, there is motion predominantly towards the center of the left ventricular chamber of the two walls, confirming previous angiographic findings. Its timing suggests that wall motion proceeds the increase in ventricular pressure.

Adult↗
PubMed1996

[Sudden cardiac death: definition, mechanisms and risk factors].

Sudden cardiac death is defined as natural death due to cardiac causes, heralded by abrupt loss of consciousness within one hour after the onset of symptoms. The mechanisms are the following: 1. ventricular fibrillation, 2. ventricular tachycardia and flutter with subsequent ventricular fibrillation, 3. torsade de pointe, 4. bradyarrhythmias and asystolic arrest. White the main risk factor is the presence of coronary artery disease, any organic or functional disease of the heart can predispose for sudden cardiac death. To evaluate the risk of sudden cardiac death noninvasive (Holter, echocardiography, exercise test and signal averaged (ECG) and often invasive (electrophysiological study) tests are necessary. The therapy is based on drugs (mainly beta blockers and amiodarone), coronary revascularization, catheter ablation techniques and the implantation of a cardioverter defibrillator; the latter appears to be the most promising approach.

Adolescent↗
PubMed1986

Long term results after operative treatment of isolated ventricular septal defect in adolescents and adults.

A series of 125 consecutive patients with isolated ventricular septal defect (VSD) aged 10 or over, were followed until death or beyond the age of 30 (31-73) years. A prospective restudy was performed after a mean follow-up of 15 (3-21) years. Forty-one patients (group 1) were treated with surgical repair of VSD at a mean age of 23 (10-51) years, and early mortality was 10%, i.e. 3 with severe aortic insufficiency and one with systemic pulmonary artery pressure. Surgery was initially not regarded indicated in 70 patients with small defects (group 2). A further 14 patients were judged inoperable (group 3). Long-term mortality was 5% in group 1, 9% in group 2 and 71% in group 3. When restudied, group 2 patients had significantly higher (p less than 0.01) and group 1, lower (p less than 0.01) pulmonary artery pressures than initially. A moderate deterioration in NYHA-rating was noted in group 2 (p less than 0.05) vs. a slight improvement in group 1 (p less than 0.05). The non-operated patients had a higher incidence of valvular lesions (19% vs. 13%) and bacterial endocarditis (4.3% vs. 2.7%) than the operated but not to a statistically significant level. Spontaneous closure was 6% in group 2 whereas mostly small residual defects were found in 34% of the operated. Patients with uncomplicated VSDs (absence of valvular lesions or coronary heart disease) had subnormal exercise tolerance as judged from a standardized ergometer bicycle test. These patients also had impaired left ventricular function based upon haemodynamic studies during moderate supine exercise. No major differences were noted between groups 1 and 2, but operated patients with residual VSDs tended to have the poorest cardiac performance. Non-cardiac disease represented only a minor problem and no significant differences in psychosocial function were observed between groups 1 and 2. Only 50% in group 1 and 60% in group 2 attended a regular medical clinic. Antibiotic prophylaxis had only been practiced by 50% in both groups. Although small, but differences between groups 1 and 2 favour surgery. This must be regarded as a positive result of surgical treatment since those operated on had basically larger and thus more severe defects than the others. In view of the very low operative risk associated with modern surgical technique one should direct patients with significant shunts to operative treatment.

Adolescent↗
PubMed1983

Systolic time intervals: a review of the method in the non-invasive investigation of cardiac function in health, disease and clinical pharmacology.

Measurement of systolic time intervals is a valuable, non-invasive procedure to assess left ventricular performance, particularly when influenced by drugs. In this review, we discuss various factors affecting systolic time intervals, the therapeutic implications of the technique and its place among other non-invasive tests of cardiac function.

Adolescent↗