Left ventricular systolic and diastolic function in aortic stenosis. Prognostic value after valve replacement and underlying mechanisms

AIMS

The aims of the study were to examine the prognostic value of pre-operative left ventricular systolic and diastolic function on early, and late mortality after valve replacement for aortic stenosis, and to identify possible underlying mechanisms.

METHODS AND RESULTS

Ninety-one prospectively recruited consecutive patients with a mean age of 61 years underwent valve replacement for aortic stenosis with concomitant coronary artery bypass grafting in 32 and a minimum postoperative observation period of 5.4 years. There were six early (< or = 30 days postoperatively) and 19 late deaths, and 18 deaths from specific causes (cardiac and prosthetic valve related). Early mortality occurred exclusively among patients with a combined subnormal left ventricular systolic function (subnormal ejection fraction or peak ejection rate, or supranormal time-to-peak ejection--duration of systole ratio) and a subnormal fast filling fraction. In Cox regression models on crude mortality and specific deaths, a subnormal ejection fraction and a fast filling fraction of < or = 45% were the only independent risk factors. Patients with none of these risk factors had normal sex- and age-specific survival, those with any one factor had an early, and those with both factors a massive early and a late excess mortality, with 5-year crude survival of 92%, 77%, and 50%, respectively (P < 0.0001). Systolic wall stress was without prognostic value. Further analyses indicated that impairment of left ventricular function occurred with increasing muscle mass over two phases: (1) diastolic dysfunction characterized by a pattern of severe relative concentric hypertrophy; (2) the addition of systolic dysfunction characterized by a more dilated, less concentric chamber geometry. Coronary artery disease seemed to provoke the latter development sooner.

CONCLUSIONS

Impaired systolic and diastolic left ventricular function, irrespective of afterload, were decisive independent pre-operative risk factors for early as well as late mortality after aortic valve replacement for aortic stenosis. The adverse influence of concentric hypertrophy was the main underlying mechanism. Operative intervention, before impairment of diastolic and systolic function, should be advocated.

Myocardial insulin resistance in patients with syndrome X

Insulin resistance is common in patients with angina pectoris, a positive exercise electrocardiogram, and normal coronary angiograms (syndrome X). It is still not known whether insulin resistance affects the cardiac muscle itself and, if so, whether insulin resistance involves myocardial hemodynamics and energy metabolism. We investigated hemodynamics as well as metabolite exchanges across the heart and the forearm in eight patients with syndrome X and eight control subjects during a baseline period after an overnight fast and during a hyperinsulinemic-euglycemic clamp. Myocardial hemodynamics and metabolism were studied at rest, during pace stress, and in the recovery period after pacing. Neither coronary sinus blood flow nor forearm blood flow differed between the groups before and during the clamp. Whole body insulin-stimulated glucose uptake was decreased in the patients (15.6+/-2.1 vs. 23.1+/-2.0 micromol x kg-1 x min-1). Insulin-stimulated glucose uptake in the forearm and the cardiac muscle was equally reduced in the patients (46+/-5 and 48+/-5%). Myocardial glucose uptake correlated with total arterial delivery in the control subjects (r = 0.63, P < 0.01), but not in patients (r = 0.22, P = 0.13). Carbohydrate and lipid oxidation was similar in the two groups at rest, and changes during the clamp were not different in control subjects and patients either at rest, during pacing, or in the recovery period. Patients with syndrome X exhibit myocardial insulin resistance, but cardiac energy metabolism remains unaffected. In patients with syndrome X, insulin-stimulated glucose uptake is independent from myocardial blood flow.

Danish multicenter randomized study of invasive versus conservative treatment in patients with inducible ischemia after thrombolysis in acute myocardial infarction (DANAMI). DANish trial in Acute Myocardial Infarction

BACKGROUND

The aim of the DANish trial in Acute Myocardial Infarction (DANAMI) study was to compare an invasive strategy of percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG) with a conservative strategy in patients with inducible myocardial ischemia who received thrombolytic treatment for a first acute myocardial infarction (AMI).

METHODS AND RESULTS

Of the 503 patients randomized to an invasive strategy, PTCA was performed in 266 (52.9%) and CABG in 147 (29.2%) from 2 to 10 weeks after the AMI. Of the 505 patients in the conservative treatment group, only 8 (1.6%) had been revascularized 2 months after the AMI. The patients were followed up from 1 to 4.5 years. The primary end points were mortality, reinfarction, and admission with unstable angina. At 2.4 years' follow-up (median), mortality was 3.6% in the invasive treatment group and 4.4% in the conservative treatment group (not significant). Invasive treatment was associated with a lower incidence of AMI (5.6% versus 10.5%; P=.0038) and a lower incidence of admission for unstable angina (17.9% versus 29.5%; P<.00001). The percentages of patients with a primary end point were 15.4% and 29.5% at 1 year, 23.5% and 36.6% at 2 years, and 31.7% versus 44.0% at 4 years (P=<.00001) in the invasive and conservative treatment groups, respectively. At 12 months, stable angina pectoris was present in 21% of patients in the invasive treatment group and 43% in the conservative treatment group.

CONCLUSIONS

Invasive treatment in post-AMI patients with inducible ischemia results in a reduction in the incidence of reinfarction, fewer admissions due to unstable angina, and lower prevalence of stable angina. We conclude that patients with inducible ischemia before discharge who have received treatment with thrombolytic drugs for their first AMI should be referred to coronary arteriography and revascularized accordingly.

Effects of ranolazine on ischemic threshold, coronary sinus blood flow, and myocardial metabolism in coronary artery disease

Cytoprotection or metabolic modulation is a new principle in the treatment of angina pectoris. The effect of ranolazine (a cytoprotective drug) on ischemic threshold, coronary sinus blood flow, and myocardial metabolism was evaluated by means of two pacing sequences in nine male patients with coronary artery disease (CAD) and in eight male controls. Ranolazine was given as an intravenous bolus followed by continuous infusion; the mean total dose was 32.7 mg and 31.7 mg in patients and controls, respectively. Angina pectoris was relieved in two patients after ranolazine but pacing time to pain was unchanged in the remaining patients. Maximal ST depression was lower (p = 0.02), but pacing time to maximal and to 1-mm ST depression remained unchanged after the drug. Ranolazine had no overall influence on coronary sinus blood flow, cardiac oxygen consumption, blood pressure, and heart rate. Cardiac uptake of free fatty acids (FFA) was reduced (p = 0.01), and net uptakes of glucose (p = 0.07) and lactate (p = 0.06) tended to be lower after ranolazine in CAD patients and controls. Ranolazine had no direct influence on cardiac exchange of glutamate, alanine, and citrate or on the arterial concentration of any metabolite. In the present study ranolazine had minimal clinical effects. A decrease in myocardial FFA utilization, however, allows greater myocardial glucose oxidation, which may increase the energy production in relation to oxygen availability.

Impact of impaired coronary flow reserve and insulin resistance on myocardial energy metabolism in patients with syndrome X

To evaluate the role of a decreased coronary flow reserve in the genesis of angina pectoris in patients with syndrome X, we studied myocardial hemodynamics and metabolism at rest, during pace stress, and in the recovery period after pacing in 18 consecutive patients with syndrome X and in 10 control subjects. By means of positron emission tomography or the intracoronary flow-wire method, patients were subclassified as having microvascular angina (MA, n = 8) when coronary flow reserve was reduced (<2.5) or no microvascular angina (non-MA, n = 10) when coronary flow reserve was preserved (> or =2.5). At rest, coronary sinus blood flow was increased in MA patients. During pace stress, coronary sinus blood flow increased by 39 +/- 6% in MA patients versus 67 +/- 12% in non-MA patients and 69 +/- 7% in controls (p <0.05). Patients with non-MA revealed fasting hyperinsulinemia, increased arterial concentration of free fatty acids, and a similar tendency for beta-hydroxybutyrate. Oxygen extraction and carbon dioxide release did not differ between groups. Net myocardial lactate release was not observed in any patient during pace stress and myocardial energy metabolism was preserved in all patients with syndrome X. During pacing, myocardial uptake of free fatty acids and beta-hydroxybutyrate was increased in non-MA patients. Myocardial uptake of free fatty acids correlated positively and myocardial glucose and lactate uptake correlated inversely with arterial concentrations of free fatty acids in all subjects. Metabolic evidence of myocardial ischemia is uncommon in patients with syndrome X, irrespective of a globally reduced coronary flow reserve. Although patients with syndrome X can be subclassified according to presence of a microvascular or a metabolic disorder, angina pectoris and ST-segment depressions coexist with a preserved global myocardial energy efficiency in all patients.

Impact of size mismatch and left ventricular function on performance of the St. Jude disc valve after aortic valve replacement

BACKGROUND

The hemodynamic function of the St. Jude valve may change relative to changes in left ventricular function after aortic valve replacement for aortic stenosis. From theoretical reasons one may hypothesize that prosthetic valve hemodynamic function is related to left ventricular failure and mismatch between valve size and patient/ventricular chamber size.

METHODS

Forty patients aged 24 to 82 years who survived aortic valve replacement for aortic stenosis with a standard St. Jude disc valve (mean size, 23.5 mm; range, 19 to 29 mm) were followed up prospectively with Doppler echocardiography and radionuclide left ventriculography preoperatively and 9 days, 3 months, and 18 months after the operation with assessment of intravascular hemolysis at 18 months. Follow-up to a maximum of 7.4 years (mean, 6.3 years) was 100% complete.

RESULTS

Left ventricular muscle mass index decreased from 198 +/- 62 g.m-2 preoperatively to 153 +/- 53 g.m-2 at 18 months (p < 0.001), paralleled by a significant increase in left ventricular ejection fraction, peak ejection rate, and peak filling rate; only 18% of the patients had normal left ventricular muscle mass index and only 32% normal ventricular function (normal left ventricular ejection fraction, peak ejection rate, peak filling rate, early filling fraction, and late filling fraction during atrial contraction) at 18 months. Prosthetic valve peak Doppler gradient dropped from 20 +/- 6 mm Hg at 9 days to 17 +/- 5 mm Hg at 18 months (p < 0.05). Reduction of left ventricular muscle mass index was unrelated to peak gradient and size of the valve. Peak gradient at 18 months rose with valve orifice diameter of 17 mm or less (by 6 mm Hg), orifice diameter/body surface area of 9 mm.m-2 or less (by 5 mm Hg), left ventricular enddiastolic dimension (by 23 mm Hg per 10 mm increase), and impaired ventricular function (by 3 mm Hg). All but 2 patients (5%) had intravascular hemolysis; none had anemia. Two patients with moderate paravalvular leak had the highest serum lactic dehydrogenase levels; 4 patients with trivial leak had higher serum lactic dehydrogenase levels than those without leak. Serum lactic dehydrogenase levels rose with moderate paravalvular leak, impaired ventricular function, and valve orifice diameter. Six patients with trivial or moderate paravalvular leak had a cumulative 7-year freedom from bleeding and thromboembolism of 44% +/- 22% compared with 87% +/- 5% for those without leak (p < 0.05).

CONCLUSIONS

The peak gradient of the St. Jude aortic valve dropped marginally over the first 18 postoperative months in association with incomplete left ventricular hypertrophy regression and marginal improvement of ventricular function. Mismatch between valve size and ventricular cavity size or patient size and impaired function of a dilated ventricle significantly compromised the performance of the St. Jude valve. Probably explained by platelet destruction or activation, paravalvular leak was related to bleeding and thromboembolic complications.

[Percutaneous transvenous balloon dilatation of mitral valve stenosis]

In this study, 42 consecutive symptomatic patients (median age 60 (30-78) years, 86% females) with mitral valve stenosis (57% had severely deformed and/or calcified mitral valves) were treated with (Inoue) balloon dilatation during the period August 1989-June 1994. Mitral valve area and cardiac output increased by 67 and 25%, whereas the transmital gradient as well as pulmonary artery pressure fell by 45% and 21%, respectively, after the dilatation. Follow-up at a mean of 16 (1-46) months revealed a total mortality of 12% (cardiac mortality of 7%). Five patients developed significant' mitral regurgitation after the treatment and four of these had subacute mitral valve replacement. A further four patients received an artificial valve during the follow-up period. During the follow-up period the increase in valve area remained unchanged, and accordingly 97% of the patients were in New York Heart Association functional class I-II. Balloon dilatation was an acceptable treatment in the described elderly population with significant mitral stenosis and deformed valves.

Glucose uptake and lumped constant variability in normal human hearts determined with [18F]fluorodeoxyglucose

BACKGROUND

Myocardial glucose uptake can be measured with [18F]fluoro-2-deoxyglucose (FDG) and positron emission tomography (PET). However, changes of myocardial metabolism may alter the ratio between the net rates of FDG and glucose uptake, known as the lumped constant. We tested the hypothesis that the variability of the lumped constant determined in animals explains the disagreement between human net myocardial glucose uptake calculated from aortocoronary sinus deficits and measured with PET.

METHODS AND RESULTS

In the three-compartment model of glucose transfer into cells, the lumped constant is a function of the relationship between the net and the unidirectional rates of uptake of glucose and glucose tracers such as FDG. Using this principle, validated in the human brain and the animal heart under experimental conditions, we estimated the lumped constant of the human heart by PET in 10 healthy men under several metabolic conditions established by altering the circulating insulin level during a euglycemic clamp and with somatostatin and heparin infusions. The lumped constant varied systematically between 0.44 and 1.35. At insulin levels below 100 pmol/L, free fatty acids were inversely related to serum insulin levels and the lumped constant increased linearly with serum insulin concentration. At insulin levels above 100 pmol/L, free fatty acids were suppressed and the lumped constant varied in inverse proportion to the insulin level. When the lumped constant was estimated in this manner, net myocardial glucose uptake agreed with that determined in previous measurements of blood flow and aortocoronary sinus deficit.

CONCLUSION

In the intact human organism, the cardiac lumped constant varies with the metabolic condition, as predicted from studies of the brain and animal heart under experimental conditions.

M-mode echocardiography in aortic stenosis. Clinical correlates and prognostic significance after valve replacement

To relate preoperative findings at M-mode echocardiography to preoperative clinical and haemodynamic status and to identify possible echocardiographic risk factors for mortality after aortic valve replacement (AVR), 250 patients with AVR for aortic stenosis (AS) were studied. In follow-up averaging 3.2 years there were 22 early (< 30 days) and 23 late deaths. Rising NYHA function class and cardiothoracic index, and left ventricular (LV) failure were related to rising LV end-diastolic and end-systolic diameter index (EDDI, ESDI), and to increasing LV muscle mass index and decreasing fractional shortening (FS). High peak-to-peak systolic aortic valve gradient and LV end-systolic pressure were related to small dimensions of LV with increased FS and posterior wall thickness (PWTh). EDDI < or = 20 mm/m2 and increasing PWTh were independent risk factors for early mortality. Patients with EDDI < or = 20 mm/m2 had normal or supranormal FS. PWTh was the only independent risk factor in long-term survival: 5-year rates being 81 +/- 6%, 94 +/- 3% and 85 +/- 7% for PWTh < or = 13, 14-17 and > or = 18 mm, respectively (p = 0.03). Prevalence of concomitant coronary artery disease (CAD) rose with decreasing PWTh. Angina pectoris in non-CAD patients was related to very high PWTh. Subnormal EDDI was associated with poor surgical outcome, and dilated, poorly contracting LV with congestive heart failure prior to AVR. The degree of LV hypertrophy seemed to be the dominant risk factor, but confounders included myocardial ischaemia due to CAD in low-grade hypertrophy or to hypertrophy per se. A hypothetically confounding factor is the reversibility potential of moderate or severe LV hypertrophy following AVR.

Haemodynamic and metabolic effects of gallopamil as additive to calcium-containing and calcium-free cardioplegic solutions in mature pig hearts

Myocardial haemodynamic and metabolic effects of the calcium-channel blocker gallopamil as additive to calcium-containing (St Thomas Hospital, STH) and calcium-free (Bretschneider procaine-containing, BRT) crystalloid cardioplegic solutions were evaluated. Adult pig hearts (weight 0.033 kg) were randomized to four groups and perfused with 1 litre of cold (4 degrees C) cardioplegic solution; group A: BRT without gallopamil, n = 9, group B: BRT with gallopamil (0.4 microM), n = 8, group C: gallopamil-free STH, n = 8, and group D: STH with gallopamil (0.4 microM), n = 8. After storage at 4 degrees C for 6 hours the hearts were reperfused with blood/Ringer solution in a modified Langendorff model for 60 min. Developed left ventricular pressure, rate-pressure product and +dP/dt were lower in gallopamil-treated hearts during reperfusion (p < 0.05), as were oxygen extraction and oxygen uptake (p < 0.05) and lactate release (p < 0.05). Myocardial blood flow was greater in gallopamil-treated hearts (p < 0.05). In hearts comparable in size and anatomy to the human heart, gallopamil added to both cardioplegic solutions reduced cardiac function and oxygen uptake despite increased myocardial blood flow. The findings suggest reduced myocardial protection after addition of gallopamil to cardioplegic solutions.

Mortality and worsening of prognostic profile during waiting time for valve replacement in aortic stenosis

In a prospective study 99 consecutive patients with operative indication due to severe aortic stenosis (AS) were put on a surgical waiting list. The waiting-time to aortic valve replacement (AVR) averaged 6.3 months (0.5-19 months). There were 58 men and 41 women with a mean age of 61 years (21-82 years). The patients were divided into three groups: group I (n = 81) with an uneventful stay on the waiting list (including one patient who declined the AVR offer); group II (n = 11) with significant worsening of a prognostic index; and group III (n = 7) with patients who died during the waiting-time. The waiting-list death rate was 13.5 +/- 5.0% patient-year-1 compared with a post-AVR death rate of 4.9 +/- 0.9%. patient-year-1 (p < 0.05) with a mean post-AVR follow-up of 5.7 years. According to their prognostic index at inclusion, group II patients had a predicted (by a Cox model) 7-year post-AVR survival probability of 72%, but only of 61% according to their prognostic index immediately preoperatively; their observed 7-year post-AVR survival was 60%. Logistic regression analysis identified high age, short duration of symptoms, severe hypertrophy and strain in the ECG, female sex, and deranged left-ventricular diastolic function (related to severely increased left-ventricular muscle mass) as independent predictors of death on the waiting-list and prognosis worsening. From a clinical viewpoint, the predictive models did not allow sufficiently accurate identification of the patients at risk during the waiting-time. The consequences of a surgical waiting-time averaging 6 months are serious for AS patients. The death rate is high and a subgroup worsen their prognostic profile, with significantly reduced post-AVR long-term survival as the result.

Effect of residual noise level on reproducibility of the signal-averaged ECG

Late potentials are detected at various noise levels in clinical studies. The aim of this study was to assess the effect of residual noise level on the reproducibility of the signal-averaged electrocardiogram (ECG). Two consecutive raw 15-minute ECG from each of 188 patients with coronary artery disease were digitized and stored on optical discs. Each raw ECG was analyzed by two signal-averaging procedures to noise level 0.2 microV or 0.4 microV. Standard time-domain parameters were measured: QRS duration (SA-QRS), late potential (LP) duration, and root-mean-square voltage of the terminal 40 ms of the filtered QRS (RMS40). The SA-QRS was prolonged by 12 +/- 14 ms by the reduction in noise level from 0.4 microV to 0.2 microV, LP duration was prolonged by 10 +/- 10 ms, and RMS40 was reduced by 19 +/- 22 microV. The temporal variation of the measured SA-QRS from ECG1 to ECG2 was significantly lower at noise level 0.2 microV (9 +/- 13 ms) than at noise level 0.4 microV (13 +/- 14 ms) (P < .001). The LP duration was also more stable at noise level 0.2 microV than at noise level 0.4 microV (0.5 +/- 11 ms vs 2 +/- 13 ms, P < .05). The presence of any two of three abnormal parameters (SA-QRS > 120 ms, RMS40 < 25 microV, LP duration > 40 ms) was used as the criterion for the presence of LPs. At noise level 0.4 microV, the proportion of patients with diagnosed LPs in ECG1 was 25% and at noise level 0.2 microV it was 62%. At noise level 0.4 microV, 20% were reclassified from LP-negative in ECG1 to LP-positive in ECG2, and 7% were reclassified from LP-positive in ECG1 to LP-negative in ECG2. At noise level 0.2 microV, 20% were reclassified from LP-negative in ECG1 to LP-positive in ECG2, and 9% were reclassified from LP-positive in ECG1 to LP-negative in ECG2. It was concluded that (1) the diagnosis of LPs is significantly dependent on the extent of noise reduction by signal averaging: and (2) the numerical reproducibility of signal-averaged QRS duration and LP duration is lower at noise level 0.4 microV then at noise level 0.2 microV; and the diagnostic reproducibility of LPs is similar at both noise levels.

Improved recovery after cold crystalloid cardioplegia using low-dose glutamate enrichment during reperfusion after aortic unclamping: a study in isolated blood-perfused pig hearts

Increased glutamate utilization is a part of the metabolic adaptation to oxygen deprivation by the heart. The effect of low-dose L-glutamate (2 mmol/L) during continuous reperfusion after aortic unclamping on postcardioplegic recovery was studied in pig hearts similar in size, anatomy, and function to the human adult heart. After cold crystalloid cardioplegic arrest (CCC) with Bretschneider solution no 3, hearts were excised from pigs weighing 70-80 kgs (heart weight, average +/- SEM: 308 +/- 4 grams), and reperfused in an isolated blood-perfused heart model for 120 minutes. Three groups of hearts were compared. One group of hearts was subjected to 30 minutes of CCC only (30 min group; n = 9), another group of hearts to 90 minutes of CCC and storage (Control group: n = 16), and a third group to 90 minutes of CCC and storage, but with L-glutamate added to the blood reperfusate (2 mmol/L) (Glutamate group: n = 18). In the Control group 14 of 16 hearts (88%) needed electrical defibrillation after start of reperfusion, significantly more (p < 0.05) than the 8 of 18 (44%) in the Glutamate group; the difference between the 30-min (2 of 9 [22%]) and the Glutamate group was not significant (p = 0.48). Developed left-ventricular pressure (DLVP) and positive dP/dtmax (+dP/dtmax) was significantly higher in the Glutamate group than in the Control group during early reperfusion (DLVP: p < 0.05: +dP/dtmax: p < 0.01) and the entire reperfusion (DLVP and +dP/dtmax: p < 0.05), while reperfusion responses in the Glutamate and 30-min groups were not significantly different. Furthermore, myocardial oxygen uptake was significantly higher in the Glutamate group than in the Control group (p < 0.001), but not higher than that in the 30-min group. Decreased lactate release was found in the Glutamate group compared to the Control group during early reperfusion (p < 0.01), and the entire reperfusion (p < 0.001). No differences were found between the Control and Glutamate groups in alanine exchange. Thus, L-glutamate has a beneficial effect in pig hearts on both functional and metabolic recovery after cold crystalloid cardioplegia and storage when present in a concentration even as low as 2 mmol/L during continuous reperfusion after aortic unclamping. A possible mechanism is a glutamate-induced stimulation of the malate-aspartate shuttle leading to increased intramyocardial lactate utilization.

Noise in the signal-averaged electrocardiogram and accuracy for identification of patients with sustained monomorphic ventricular tachycardia after myocardial infarction

Late potentials are detected at various noise levels in clinical studies. The aim of this study was, in a case-control design, to assess the effect of residual noise level on the identification of patients with sustained monomorphic ventricular tachycardia after myocardial infarction. Electrocardiograms from 16 patients with prior myocardial infarction and documented sustained monomorphic ventricular tachycardia and 41 patients with prior myocardial infarction and without ventricular tachycardia, were analysed by two signal averaging procedures to noise level 0.2 and 0.4 muV. Standard time domain parameters were measured. Two definitions of late potential were analysed: (1) if any two of the following criteria were present (signal-averaged QRS duration > 120 ms, late potential duration > 40 ms, and root-mean-square voltage of the terminal 40 ms of the filtered QRS < 25 muV); or (2) if the signal-averaged QRS duration > or = 120 ms. Overall the signal-averaged electrocardiogram performed better at noise level 0.4 muV compared to noise level 0.2 muV with respect to identification of patients with or without ventricular tachycardia after myocardial infarction. Reducing noise level from 0.4 to 0.2 muV increased the sensitivity, but the consequence was a substantial decrease in specificity. Our data indicate that when a high sensitivity is the goal, the definition based only on signal-averaged QRS duration > or = 120 ms should be applied; sensitivity was 88% and specificity 59% at noise level 0.4 muV. If a high specificity is the goal, the definition should be based on the definition with two abnormal parameters; sensitivity was 69% and specificity 68% at noise level 0.4 muV.

The potential for normal long term survival and morbidity rates after valve replacement for aortic stenosis

BACKGROUND AND AIM OF THE STUDY

The sequelae of early aortic valve replacement (AVR) for aortic stenosis (AS) are controversial, with an increasing body of opinion regarding the patient risk profile as having an influence on long term survival and prosthesis-related morbidity rates. We therefore undertook a comparison of the morbidity and mortality rates of the patients undergoing AVR at our institution over a 22 year period with those in the background population to establish whether early intervention leads to an increased incidence of either.

METHODS

A multivariate risk analysis of 630 consecutive patients with AS who were alive 30 days after AVR performed between January 1965 and December 1986 was completed. The patients had a mean age of 59 years (range 14-78 years), 98% received a mechanical prosthetic valve, and 71% were in functional classes III or IV preoperatively.

RESULTS

Relative to an age- and sex-matched background population, the patients suffered a slight excess mortality during the first postoperative year, and a significant excess mortality after the 12th year, which was primarily related to congestive heart failure (64% of deaths versus 25% during the first 12 years; p < 0.01). A multivariate Cox regression model allowed calculation of a prognostic index for each patient. The index divided the patients into three groups (from low to high index): group A (n = 195) had normal sex- and age-specific survival, group B (n = 165) had a slight late (> 12th year) excess mortality, while group C (n = 270) had significant excess mortality throughout the follow up. Multivariate risk analysis of thromboembolism (1.7%/pt-yr), anticoagulant related hemorrhage (1.5%/pt-yr), all prosthesis-related complications combined (4.2%/pt-yr), and sudden cardiac events (arrhythmia and myocardial infarct; 1.8%/pt-yr) identified variables underlying advanced preoperative heart disease, coronary artery disease and systemic hypertension as the decisive risk factors. The preoperative prevalence of these risk factors as well as the postoperative incidence of the complications differed significantly between the three patient groups; A < B < C. Incidence rates of stroke in the patients (95% confidence interval) and in sex- and age-matched background populations were: group A, 0.48 (0.13-0.83) and 0.34 %/pt-yr, respectively, group B, 1.07 (0.46-1.68) and 0.52%pt-yr, respectively, and group C, 2.28 (1.50-3.06) and 0.68%/pt-yr respectively. Similar results were obtained for incidence rates of myocardial infarct.

CONCLUSION

Operative intervention early in the course of AS, being equivalent to a favorable risk profile, may result in an age- and sex-specific normal long term survival, generally low rates of prosthesis-related complications and a normal incidence of the dominant thromboembolic and hemorrhagic events and of myocardial infarction.

The signal-averaged ECG becomes late potential-positive at low noise levels in healthy subjects

Late potentials are detected at various noise levels in clinical studies. The aim of this study was to quantify the effect of residual noise level on the signal-averaged ECG. Thirty minutes of raw ECG (lead -X, +X, -Y, +Y, -Z, and +Z) from 10 healthy volunteers were digitized and stored on optical discs. Each ECG was analysed by four signal averaging procedures to noise level 0.1, 0.2, 0.3, and 0.4 microV, respectively. At each noise level, time domain analysis of the filtered vector (40-250 Hz) included determination of the QRS duration (QRS), late potential duration (LPD, duration of terminal signals below 40 microV), and root-mean-square voltage of the terminal 40 ms of the filtered QRS (RMS40). On average, the measured signal-averaged QRS duration was prolonged by 7.0 ms (range 0.9-12.5 ms) per 0.1 microV reduction in noise level. Late potential duration increased by 5.9 ms (range 0.2-10.0 ms) per 0.1 microV reduction in noise level, and RMS40 was reduced by 9.1 microV (range 0.5-20.2 microV) per 0.1 microV reduction in noise level. At noise level 0.4 microV, 0.3 microV, 0.2 microV, and 0.1 microV the number of late potential-positive subjects were 1, 2, 4, and 6, respectively. Late potential parameters are significantly dependent on noise level after signal averaging. Using conventional criteria for late potentials, healthy subjects become false-positive at low noise levels. Establishment of standards for noise level is recommended.

Applicability of small endomyocardial biopsies for evaluation of high energy phosphates and glycogen in the heart

To evaluate variability of biochemical determination of energy stores in endomyocardial biopsies, we compared myocardial contents of high energy phosphates and glycogen in endomyocardial and transmural myocardial biopsies from 12 75-kg pigs before, during, and after cardioplegia. Before cardioplegia, comparable amounts of adenine nucleotides and glycogen were found in left and right ventricular endomyocardial and left ventricular transmural biopsies. Phosphocreatine levels were lower in endomyocardial than in transmural biopsies. Significant correlations were observed between endomyocardial and transmural adenine nucleotide and glycogen contents but not phosphocreatine content. During cardioplegia, myocardial ATP and phosphocreatine contents increased and glycogen concentration tended to decrease. During reperfusion, ATP and glycogen levels decreased, whereas phosphocreatine levels increased remarkably. Transmural changes in left ventricular adenine nucleotide and glycogen levels were reflected in endomyocardial biopsies but those in phosphocreatine were not. By increasing the number of endomyocardial biopsies from one to three, within-subject variance was reduced from 33-47% to 14-23% of total variance whereas four or more biopsies only added minor further reduction in variability. In conclusion, endomyocardial biopsies yield representative estimates of the average myocardial content of adenine nucleotides and glycogen but not of phosphocreatine in the normal heart. Endomyocardial biopsies offer a sensitive estimate of the changes in myocardial adenine nucleotides and glycogen induced by cardioplegia and reperfusion. However, metabolite content in endomyocardial biopsies shows a high variability. Three or more endomyocardial biopsies are necessary to reduce variability to acceptable levels.

Superiority of acid extractable glycogen for detection of metabolic changes during myocardial ischaemia

Various methods for extraction and isolation of myocardial glycogen show different yields and identify different glycogen subsets. The aim of the present study was to identify a glycogen fraction exposed to changes during myocardial ischaemia. Endomyocardial biopsies from 10 pigs were sampled before cardioplegia, after cardioplegic arrest, and after reperfusion. Glycogen yields were compared following five extraction procedures: (1) hot alkaline tissue digestion, (2) homogenization in perchloric acid and subsequent determination in homogenate, (3) homogenization in perchloric acid and subsequent determination in supernatant, (4) homogenization in perchloric acid and subsequent determination in the precipitate redissolved in hot alkaline and (5) homogenization in homogenisation buffer with lysating capacity. Glycogen was isolated on filter-paper and determined enzymatically. Hot alkaline tissue digestion yielded the highest glycogen amounts (63.5 +/- 18.3 nmol/mg wet weight). Glycogen yields in perchloric homogenate and supernatant were 51%, perchloric precipitate 47%, and buffer 30% of these obtained with hot alkaline. Glycogen yields in hot alkaline were comparable to the sum of those obtained in perchloric supernatant ("acid extractable glycogen") and redissolved precipitate ("heavily extracted glycogen") confirming that glycogen yields obtained with hot alkaline digestion represent "total glycogen". Acid extractable glycogen showed superior analytical characteristics compared with the other methods. Acid extractable glycogen demonstrated a consistent decrease during ischaemia whereas total glycogen and glycogen extracted in homogenization buffer tended to decrease. Glycogen in perchloric precipitate remained unchanged during ischaemia. These findings support a revival of the concept that tissue contains two forms of glycogen. Decreases in myocardial glycogen content during myocardial ischaemia are best observed with acid extractable glycogen.

[Intracoronary ultrasonography--a supplement to coronary arteriography]

Intracoronary ultrasound is a new technique, by means of which it is possible for the first time to visualise coronary artery wall structures in vivo. Compared to conventional coronary angiography the advances of this new modality appear to be: 1) Improved diagnosis of minimal and non-obstructive atherosclerosis; 2) Characterisation of plaque morphology, thereby being an aid in decision on interventional procedures (PTCA, atherectomy, stent placement); 3) Better delineation of coronary artery lumen area, which improves the accuracy of stenosis graduation both before and after interventional procedures. The examination can be performed in up to 95% of cases. The procedure appears to be safe with a reported complication rate of myocardial infarction and bypass surgery of 0.16% in 1837 cases; transient coronary artery spasms occurred in about 3%. Complications are predominantly associated with interventional procedures. Although intracoronary ultrasound has mainly been used for research purposes, results of ongoing trials assessing its clinical utility, as well as technological improvement providing more consistent image quality, suggest that the procedure will evolve into an important adjunct to coronary angiography.

Short- and long-term survival after aortic balloon valvuloplasty for calcified aortic stenosis in 137 elderly patients

Percutaneous transluminal balloon aortic valvuloplasty was performed in 137 patients with symptomatic severe calcified aortic stenosis (50 men and 87 women, mean age 77 years) between December 1986 and September 1990. The purpose of the study was to evaluate short- and long-term survival after balloon aortic valvuloplasty, mean follow-up was 19 months. At the time of balloon aortic valvuloplasty congestive heart failure (NYHA III-IV) was present in 89%, angina pectoris in 47%, and syncope in 31% of the patients. Aortic balloon dilatation produced significant decreases in peak pressure gradient from 91 +/- 34 mmHg to 40 +/- 26 mmHg (p < 0.001). The procedure related mortality was 8% (11 pts) and the 30-days mortality 17% (23 pts). Severe complications occurred in 25% of the patients during the procedure and within the first 24 hours. Immediate clinical improvement was noted in 68% of the patients surviving the treatment. The overall survival rate was at one, two, three and four years follow-up 63%, 40%, 28%, and 21%, respectively. These survival rates were all statistically different from the survival rates in an age- and sex-matched background population (p < 0.001). A multivariate Cox analysis revealed that only female sex and angina before treatment seemed to improve survival.

CONCLUSION

The long-term outcome after aortic balloon valvuloplasty for severe aortic stenosis is so poor that we recommend aortic valve replacement as the initial treatment in these patients, if at all possible.

Determination of high energy phosphates and glycogen in cardiac and skeletal muscle biopsies, with special reference to influence of biopsy technique and delayed freezing

OBJECTIVE

The aim was to clarify the influence of biopsy technique and the effects of temporal delay between sampling and freezing on tissue contents of labile metabolites.

METHODS

Cardiac and skeletal muscle concentrations of adenine nucleotides, phosphocreatine, creatine, and glycogen in pigs were determined in endomyocardial and transmural myocardial biopsies and in skeletal muscle biopsies obtained with either endomyocardial bioptome or Tru-cut needle. The influence of the temporal delay between biopsy sampling and freezing was evaluated by keeping the biopsies at room temperature for varying intervals up to 300 s before freezing.

RESULTS

Skeletal muscle showed higher concentrations of creatine compounds and lower contents of ADP and AMP than cardiac muscle, whereas ATP, total adenine nucleotide pool, and glycogen were similar. Lower phosphocreatine contents were found both in endomyocardial biopsies and in skeletal muscle biopsies obtained with bioptome compared to transmural myocardial biopsies and skeletal muscle biopsies obtained with Tru-cut needle, respectively. Other metabolites were unaffected by the biopsy technique. With extended delays between biopsy sampling and freezing, an increase in skeletal muscle phosphocreatine averaging 26% after 5 min was observed. In the heart, a decrease in glycogen content averaging 42% after 5 min was found. These changes were not related to the biopsy procedure and were not observed within the period usually required to freeze biopsies in experimental as well as clinical settings.

CONCLUSIONS

There are essential metabolic differences between cardiac and skeletal muscle. Low endomyocardial phosphocreatine levels are influenced by the biopsy technique, compromising the use of endomyocardial biopsies for establishing myocardial phosphocreatine content. Reliable measurements of adenine nucleotides and glycogen can be obtained with endomyocardial biopsies.

Analytical evaluation of high energy phosphate determination by high performance liquid chromatography in myocardial tissue

High performance liquid chromatography (HPLC) is an established method for the determination of myocardial high energy phosphates (HEP). Quantification of HEP compounds in small tissue specimens obtained by endomyocardial biopsy technique requires maximal sensitivity without impairment of precision. Employing isocratic ion-pair reversed-phase HPLC, high sensitivity and precision were obtained by running analyses for adenonucleotides and creatine compounds separately at detection wavelengths of 254 and 210 nm, respectively. Further reasons for separate runs were given by the necessity for different sample preparation as remaining perchloric ion after deproteinizing and pH in the samples had various effects on adenonucleotides and creatine compounds. Mechanical homogenization for 20 s in 0.42 mol/l perchloric acid ensured a consistent myocardial HEP extraction. Sample preparation directly following biopsy sampling is preferable since HEP compounds were labile in tissue within days at -80 degrees C even though an initial metabolic inhibition in liquid nitrogen had been induced. Following extraction and neutralization, HEP compounds were stable for up to 3 months at -20 degrees C.

Comparison of non-collagen protein and total creatine as reference for determination of energy stores in endomyocardial biopsies

OBJECTIVE

The aim was to establish a reliable reference system for biochemical measurements in endomyocardial biopsies.

METHODS

Myocardial tissue samples were obtained from pigs before and after cardioplegic arrest and reperfusion. Non-collagen protein content was evaluated as a non-specific reference system and compared with total creatine content representing a specific myocardial reference system. The influence of base strength, extraction temperature, and extraction time on protein yields was determined in tissue precipitates redissolved in NaOH. Interference from protein of collagenous origin was excluded by hydroxyproline determinations. Variability of myocardial ATP content in relation to non-collagen protein and total creatine was compared in endomyocardial biopsies taken before and after cardioplegic arrest and reperfusion.

RESULTS

The two methods showed comparable analytical precision. Apart from an interference in 1.0 mol.litre-1 NaOH for extended extraction periods at high temperatures, myocardial protein yields increased with increasing base strength, extraction temperature, and extraction time. During cardioplegic arrest and reperfusion heart weight increased due to oedema. Simultaneously, myocardial non-collagen protein content decreased. No change in total creatine was found during cardioplegic arrest but there was a significant loss of creatine after reperfusion. Comparison of variability in myocardial ATP content with non-collagen protein or total creatine as reference systems revealed no difference.

CONCLUSIONS

Determination of non-collagen protein can be optimised with standardised conditions for protein extraction in tissue precipitates. Employment of total creatine as a reference system does not reduce variability of myocardial metabolite determinations in endomyocardial biopsies compared with non-collagen protein. Loss of myocardial creatine may in itself provide additional information about myocardial injury but this makes it unsuitable as a reference system for measuring metabolic changes during reperfusion. Multiple biopsies seem necessary for estimation of myocardial energy stores.

[Fatal hemostatic complications following erroneous thrombolytic therapy in patients with suspected acute myocardial infarction]

This report describes the fate of two young men wrongly treated with thrombolysis for suspected myocardial infarction. Both had electrocardiographic changes upon admission. Correct diagnoses of aortic dissection and haemorrhagic pericarditis was obtained within a few hours, but, due to the prolonged disturbance of haemostasis, appropriate therapy could not be instituted, and outcome was fatal for both patients. These cases underline the importance of rigid ST criteria, and procedures for neutralization of thrombolysis are proposed.

Myocardial loss of glutamate after cold chemical cardioplegia and storage in isolated blood-perfused pig hearts

Metabolic adaptation of the ischemic human heart includes release of lactate, augmented uptake of glucose and glutamate, together with increased release of citrate and alanine. In the present study exchanges of these metabolites were examined in relation to left ventricular function (LVF) in pig hearts during reperfusion after hypothermic cardioplegic-induced global ischemia and storage. Three groups of pig hearts were studied. Group I consisted of 11 hearts subjected to 9 minutes of warm ischemia prior to cold chemical cardioplegia with Bretschneider's cardioplegic solution (CCC), and hypothermic storage (HS), for a total of 180 minutes. Groups II and III, 8 hearts in each, were subjected to 90 and 180 minutes of CCC and HS, without precardioplegic warm ischemia. All hearts were reperfused in an isolated blood-perfused Langendorff model. Myocardial oxygen uptake and LVF were two-fold depressed in Group I compared to Groups II and III during the first 25 minutes of reperfusion. An increased uptake of glucose (p < 0.05) and augmented release of lactate (p < 0.01) and citrate (p < 0.001) were found during the reperfusion period in the hearts subjected to precardioplegic warm ischemia, indicating an increased total ischemic burden compared to Groups II and III. No significant changes in LVF or myocardial metabolism were noted between Groups II and III during reperfusion. In all three heart groups a substantial release or loss of glutamate was found at start of reperfusion, although in the preischemic state prior to cardioplegia pig hearts were found to extract glutamate from the circulation to an extent similar to that of the human heart.(ABSTRACT TRUNCATED AT 250 WORDS)