Hemodynamic evaluation of intra-aortic balloon pumping in man

Management of post-myocardial infarction ventricular septal defects: A critical assessment

BACKGROUND

Post-myocardial infarction (MI) ventricular septal defects (PIVSD) are an uncommon but life-threatening complication of acute MI. Although surgical closure has been the standard of care, mortality, and recurrence of VSD remain high even after emergent surgery. Transcatheter VSD closure (TCC) devices have become an alternative or adjunct to surgical closure.

METHODS

Online database search was performed for studies that included adults with PIVSD who underwent medical treatment (MT) alone, surgical closure (SC) (early or late), and TCC (early, late, or for post-surgical residual VSD).

RESULTS

Twenty-six studies were included with a total of 737 patients who underwent either MT (N = 100), SC (early (n = 167), late (n = 100)), and TCC (early (n = 176), late (n = 115), or post-surgical residual VSD (n = 79)). The 30-day mortality among MT group was 92 ± 6.3%, among SC was 61 ± 22.5% (early 56 ± 23%, late 41 ± 30%), and for all TCC patients was 33 ± 24% (early 54 ± 32.7%, late 16 ± 26%), and TCC for post-surgical residual VSD 11 ± 34.9%. The mortality among overall SC, overall TCC and early TCC groups was significantly lower as compared with the MT (P < 0.001 for all comparisons). The overall mortality among all TCC, and late TCC groups was significantly lower when compared with the late SC (P < 0.0001, P < 0.0001, respectively).

CONCLUSION

Closure of PIVSD decreases mortality as compared with MT alone and should be attempted as early as possible after diagnosis. Selection of TCC versus SC should be based on factors including complexity of the defect, availability of closure devices, expertise of the operator, and clinical condition of patient.

IABP: history-evolution-pathophysiology-indications: what we need to know

Treatment with the intraaortic balloon pump (IABP) is the most common form of mechanical support for the failing heart. Augmentation of diastolic pressure during balloon inflation contributes to the coronary circulation and the presystolic deflation of the balloon reduces the resistance to systolic output. Consequently, the myocardial work is reduced. The overall effect of the IABP therapy is an increase in the myocardial oxygen supply/demand ratio and thus in endocardial viability.

This is an overall synopsis of what we need to know regarding IABP. Furthermore, this review article attempts to systematically delineate the pathophysiology linked with the hemodynamic consequences of IABP therapy. The authors also look at the future of the use of the balloon pump and conclude that the positive multi-systemic hemodynamic regulation during IABP treatment should further justify its use.

Intra-Aortic Balloon Pump Counterpulsation in the Post-Resuscitation Period is Associated with Improved Functional Outcomes in Patients Surviving an Out-of-Hospital Cardiac Arrest: Insights from a Dedicated Heart Attack Centre

BACKGROUND

Despite advances in cardiopulmonary resuscitation, functional survival remains low after out-of-hospital cardiac arrest (OOHCA). Intra-aortic balloon pump (IABP) therapy has recently been shown to augment cerebral blood flow. Whether IABP therapy in the post-resuscitation period improves functional outcomes is unknown.

METHODS

We analysed 174 consecutive patients who were successfully resuscitated from an OOHCA between 2011-2013 at Harefield Hospital, London. We analysed functional status at discharge and mortality up to one year.

RESULTS

A total of 55 patients (32.1%) received IABP therapy. Comparing those receiving IABP with those not receiving IABP, there was no difference in favourable functional status at discharge (49.1% vs. 57.1%, p=0.321); and mortality at one year (45.5% vs. 35.5%, p=0.164). Multivariable analyses identified IABP therapy as a strong independent predictor for favourable functional status at discharge (OR=7.51, 95% CI: 2.15-26.14, p=0.002) and this association was maintained in propensity-score adjusted analyses (OR=9.90, 95% CI: 2.11-46.33, p=0.004) and inverse probability treatment weighted analyses (OR=10.84, 95% CI: 2.75-42.69, p<0.001). However, IABP therapy was not an independent predictor for mortality at one year (HR=0.93, 95% CI: 0.52-1.65, p=0.810) and this was confirmed in both propensity-score adjusted and inverse probability treatment weighted analyses.

CONCLUSIONS

In this observational analysis of patients surviving an OOHCA, the use of IABP therapy in the post-resuscitation period was associated with improved functional outcomes. This warrants further evaluation in larger prospective studies.

Percutaneous Left Ventricular Assist Devices

Percutaneous left ventricular assist devices (P-LVADs) can be life saving and may permit the stabilization of a patient in cardiovascular collapse who would otherwise face imminent demise. For specific patients and clinical indications, or where a greater degree of hemodynamic support is required, numerous studies have demonstrated the feasibility and safety of the newer generation P-LVADs. The potential applications for P-LVADs have continued to expand, now including diverse uses such as support for cardiogenic shock, bridge to and following cardiac surgery, and more novel applications such as complex electrophysiologic mapping and ablation studies of unstable ventricular rhythms.

Chronic heart failure: contemporary diagnosis and management

Chronic heart failure (CHF) remains the only cardiovascular disease with an increasing hospitalization burden and an ongoing drain on health care expenditures. The prevalence of CHF increases with advancing life span, with diastolic heart failure predominating in the elderly population. Primary prevention of coronary artery disease and risk factor management via aggressive blood pressure control are central in preventing new occurrences of left ventricular dysfunction. Optimal therapy for CHF involves identification and correction of potentially reversible precipitants, target-dose titration of medical therapy, and management of hospitalizations for decompensation. The etiological phenotype, absolute decrease in left ventricular ejection fraction and a widening of QRS duration on electrocardiography, is commonly used to identify patients at increased risk of progression of heart failure and sudden death who may benefit from prophylactic implantable cardioverter-defibrillator placement with or without cardiac resynchronization therapy. Patients who transition to advanced stages of disease despite optimal traditional medical and device therapy may be candidates for hemodynamically directed approaches such as a left ventricular assist device; in selected cases, listing for cardiac transplant may be warranted.

Effects of intra-aortic balloon counterpulsation in a model of septic shock

BACKGROUND

Fluid refractory septic shock can develop into a hypodynamic cardiovascular state in both children and adults. Despite management of these patients with empirical inotropic therapy (with or without a vasodilator), mortality remains high.

OBJECTIVES

The effect of cardiovascular support using intra-aortic balloon counterpulsation was investigated in a hypodynamic, mechanically ventilated canine sepsis model in which cardiovascular and pulmonary support were titrated based on treatment protocols.

METHODS

Each week, three animals (n = 33, 10-12 kg) were administered intrabronchial Staphylococcus aureus challenge and then randomized to receive intra-aortic balloon counterpulsation for 68 hrs or no intra-aortic balloon counterpulsation (control). Bacterial doses were increased over the study (4-8 x 10(9) cfu/kg) to assess the effects of intra-aortic balloon counterpulsation during sepsis with increasing risk of death.

MAIN RESULTS

Compared with lower bacterial doses (4-7 x 10(9) colony-forming units/kg), control animals challenged with the highest dose (8 x 10(9) colony-forming units/kg) had a greater risk of death (mortality rate 86% vs. 17%), with worse lung injury ([A - a]O2), and renal dysfunction (creatinine). These sicker animals required higher norepinephrine infusion rates to maintain blood pressure (and higher FIO2) and positive end-expiratory pressure levels to maintain oxygenation (p < or = 0.04 for all). In animals receiving the highest bacterial dose, intra-aortic balloon counterpulsation improved survival time (23.4 +/- 10 hrs longer; p = 0.003) and lowered norepinephrine requirements (0.43 +/- 0.17 microg/kg/min; p = 0.002) and systemic vascular resistance index (1.44 +/- 0.57 dynes/s/cm5/kg; p = 0.0001) compared with controls. Despite these beneficial effects, intra-aortic balloon counterpulsation was associated with an increase in blood urea nitrogen (p = 0.002) and creatinine (p = 0.12). In animals receiving lower doses of bacteria, intra-aortic balloon counterpulsation had no significant effects on survival or renal function.

CONCLUSIONS

In a canine model of severe septic shock with a low cardiac index, intra-aortic balloon counterpulsation prolongs survival time and lowers vasopressor requirements.

Use of the internal mammary artery graft and in-hospital mortality and other adverse outcomes associated with coronary artery bypass surgery

BACKGROUND

There is clear evidence that patients having coronary artery bypass graft surgeries with an internal mammary artery (IMA) have better long-term survival. Some studies have suggested a short-term protective effect as well but, because older and sicker patients are less likely to receive an IMA graft, there has been concern that the apparent protective effect of the IMA on short-term mortality has been confounded by other risk factors. This study was intended to examine the independent effect of IMA grafts on in-hospital mortality while adjusting for patient and disease factors.

METHODS AND RESULTS

We studied the use of the left IMA (LIMA) in 21 873 consecutive, isolated, first-time coronary artery bypass graft procedures from 1992 through 1999. A total of 87% of the patients received a LIMA graft. LIMA graft use was associated with a significantly decreased risk of mortality. The crude odds ratio for death (LIMA versus no LIMA) was 0.26 (95% confidence intervals, 0.22, 0.31; P:<0.001). LIMA grafts were protective across all major patient and disease subgroups. The odds ratios by subgroup ranged from 0.13 to 0.48. After adjustment for all major risk factors, the odds ratio for death was 0.40 (95% confidence intervals, 0.33, 0.48; P:<0.001). Rates of cerebrovascular accident, return to cardiopulmonary bypass, return to the operating room for bleeding, and mediastinitis or sternal dehiscence requiring surgery were also less in the LIMA group, although not significantly so.

CONCLUSIONS

These data suggest that in addition to its well-documented patency and long-term beneficial effect, LIMA grafting has a strong protective effect on perioperative mortality.

Predictors of survival 1 hour after implantation of an intra-aortic balloon pump in cardiac surgery

From July 1996 to March 2000, 391 patients with intraoperative cardiac low-output syndrome who underwent surgery with heart-lung bypass and had an intra-aortic balloon pump (IABP) implanted were analyzed in a prospective study. Of these 391 patients, 153 (39%) were operated on in an emergency situation, and 238 (61%) patients had elective surgeries. The perioperative mortality was 34% (133 patients). Clinical parameters were analyzed 1 hour after IABP support began. Statistical multivariate analysis showed that patients with an adrenaline requirement higher than 0.5 microg/kg/min, a left atrial pressure higher than 15 mmHg, output of less than 100 mL/hour, and mixed venous saturation (SvQ2) of less than 60% had poor outcomes. Using this data, we developed an IABP score to predict survival early after IABP implantation in cardiac surgery. We conclude that the success or failure of perioperative IABP support can be predicted early after implantation of the balloon pump. In patients with low-output syndrome despite IABP support, implantation of a ventricular assist system should be considered.

Fatal haemorrhage following intra-aortic balloon counterpulsation: a case report and a brief review of its clinico-pathological and medico-legal aspects

Intra-aortic balloon counterpulsation may result in serious and possibly fatal vascular complications, such as arterial dissection, in as many as 20 per cent of cases. A significant proportion of these complications may go unrecognized clinically. The following is an account of such a case from Singapore in which an elderly patient with a history of severe ischaemic heart disease died within 25 hours of coronary bypass surgery (resulting from massive intraperitoneal haemorrhage), as a consequence of post-operative intra-aortic balloon counterpulsation. The clinico-pathological and medico-legal aspects of the case are also discussed, together with a brief mention of the role of post-mortem coronary angiography in assessing venous graft patency and integrity.

Algorithm to identify components of arterial blood pressure signals during use of an intra-aortic balloon pump

Existing bedside cardiovascular monitors often inaccurately measure arterial blood pressure during intra-aortic balloon pump (IABP) assist. We have developed an algorithm that correctly identifies features of arterial pressure waveforms in the presence of IABP. The algorithm is adaptive, functions in real-time, and uses information from the electrocardiographic (ECG) and arterial blood pressure signals to extract features and numeric values from the arterial blood pressure waveform. In its current form, it requires reliable ECG beat detection and was not intended to operate under conditions of extremely poor balloon timing. The algorithm was evaluated by an expert (P.F-C.) on a limited data set, which consisted of 12 1-minute epochs of data recorded from 6 intensive care unit patients. A criterion for selection of patients was that the ECG beat detector could detect ECG beats correctly from the waveforms. The overall sensitivity and positive predictivity for beat detection were 94.04% and 100%, respectively. For feature identification, the overall sensitivity was greater than 89%, positive predictivity was 100%, and the false-positive rate was 0%. The performance measures may be biased by the criteria for patient selection. This approach to identifying waveform features during IABP improves the accuracy of measurements. The utility of using 2 sources of information to improve measurement accuracy has been demonstrated and should be applicable to other physiologic signal-processing applications.

Enhancing the applicability and effectiveness of intraaortic balloon counterpulsation

Severe maneuvers designed to enhance the applicability and effectiveness of intraaortic balloon pulsation are presented. (1) Insertion of balloon catheter directly into the ascending aorta. The technique uses an indwelling silastic snare that allows direct insertion of a balloon catheter into the ascending aorta in the course of open heart operations without the necessity of returning the patient to the operating room and reopening the chest at the time of balloon catheter removal. (2) Elimination of electric artifacts in the course of intraaortic balloon assist. A method is presented that utilizes optical rather than electric signals to operate the intraaortic balloon pump and eliminates pacer interference as well as other electrical artifacts. (3) Enhancing assist effectiveness by balloon positioning. In a series of clinical observations, it was found that the effectiveness of balloon assist may be enhanced by as much as 75% by appropriate positioning. The previously held concept that placing the balloon in a subclavian location is optimal is challenged and it is recommended that the proper position of the balloon catheter be determined by using appropriate hemodynamic measurements in different locations. (4) Control of bleeding following removal of percutaneously inserted transfemoral balloon catheter. The technique utilizes a balloon catheter which is introduced into the puncture hole of the femoral artery after minimal surgical dissection and allows direct suturing of the bleeding source.

Critical care transportation medicine: new concepts in pretransport stabilization of the critically ill patient

Regionalization of health care for trauma has become commonplace, and the same concept for critically ill medical/surgical patients is developing. Recent evidence suggests that current stabilization measures used by transport teams can be inadequate for this critically ill patient population. In trauma, speed has been considered a necessity to get the patient to a facility which cannot be carried out to the field, eg, an operating room. For acute medical illnesses, critical care transport teams can bring intensive care technology to the patient. Accumulating evidence supports the premise that speed of transport is not as important as stabilization before transport, knowledge of hemodynamics during transport, and early use of critical care monitoring systems. Other reports identify the need for initial evaluation and stabilization of critically ill patients by physicians at the critical care level of expertise. Accordingly, critical care transportation teams have evolved, creating new notions of pretransport stabilization not applicable to previous transport systems.

A closed-loop control scheme for intraaortic balloon pumping

The beneficial hemodynamic effects of IABP are critically dependent on balloon timing relative to the diastolic phase of the cardiac cycle. A microprocessor-based controller has been developed to implement real-time automation of IABP using P-R intervals to regulate balloon deflation and systolic time intervals to trigger balloon inflation in a semi-automatic fashion. Experiments were performed on anesthetized open-chest dogs. Simultaneous measurement of aortic pressure and flow, coronary flow, and left ventricular pressure were recorded. Muscle segment lengths in normal and ischemic border zones were also measured from implanted pairs of endocardial ultrasonic dimension gages. P-waves were obtained from atrial cardiograms, and heart sounds were detected using a special filtering circuit. Both signals were input together with ECG to automate IABP timing. Systolic time intervals were calculated in real-time. IABP efficacy was assessed from changes in aortic flow, coronary flow, tension time index, end diastolic pressure, and the endocardial viability ratio. Comparisons were made between automated and manual timing set by a certified technician. Results indicate that automated timing yielded equivalent hemodynamic enhancement with greater ease of adjustment. A closed-loop control scheme is proposed which allows complete automatic device operation and the capability to rapidly achieve the optimum of any directly measurable hemodynamic variable.

Intra-aortic balloon counterpulsation. Clinical experience

From March 1975 until September 1978, seventy patients were referred for intra-aortic balloon counterpulsation for cardiogenic shock complicating acute myocardial infarction or for the treatment of low cardiac output states following cardiopulmonary bypass. Sixty of these received adequate intra-aortic balloon pump assistance; fifty-two ped successfully off the balloon pump. Twenty-three patients survived to leave hospital.