The patient is hypotensive is this Pump Failure?

Does the Heart Contract Normally (is this pump failure)?

There are innumerable causes of cardiogenic shock. You must think about inflow obstruction (cardiac tamponade – jugular veins distend on inspiration and heart sounds cannot be heard), outflow obstruction (pulmonary embolism) and pump failure (acute ischemia or volume overload). There are a medley of clinical signs to fit each diagnosis (e.g. pulmonary embolism – tachycardia, right ventricular strain, hypoxemia and hypocarbia, deep venous thrombosis). It may be necessary to construct, mentally, cardiac pressure volume curves, to optimize cardiac filling, and avoid excessive stretch of myofibrils.

Table 1: shock states and hemodynamic manifestations

Problems with ejection (systolic dysfunction) include pump failure and outflow obstruction

Pump failure is caused by ischemia, overload, contusion, inflammation

1. Problems with the pump itself: the heart is a muscle, and if there is damage to the muscle it will not pump effectively. This may be due to inadequate functioning muscle mass, as occurs with ischemia, contusion (bruising in trauma), inflammation (myocarditis) and fibrosis, or to excessive stretch, with excessive fluid administration or valvular incompetence (e.g. aortic regurgitation). With each of these, confirmatory evidence may be available, electro-cardiographic or echocardiographic evidence of acute ischemia. The patient may give a good history of chest pain or trauma, cardiac enzymes may be positive, and murmurs may be audible. Do not forget the right ventricle: right ventricular contusion or infarction may be much more difficult to diagnose and the treatment is almost the polar opposite of that of left ventricular failure. The pump may be overwhelmed by excessive volume administration, or valvular (aortic or pulmonary) regurgitation.

• Cardiac outflow obstruction is caused by  pulmonary embolism, aortic stenosis, aortic crossclamps

2. Outflow obstruction: there are two major sites that cardiac outflow may be blocked: at the level of the aortic valve (aortic stenosis) or within the low pressure (at thus easily occluded)

pulmonary circulation – pulmonary embolism. The former can be diagnosed on the basis of history, ECG and classic murmur. The latter may be more difficult to diagnose. Useful information includes risk (cancer, immobility, deep venous thrombosis, lack of prophylaxis, pelvic and hip surgery), ECG changes (right sided – RVH, sinus tachycardia, atrial fibrillation, right bundle branch block), occasional chest x-ray findings, and definitive diagnosis on ventilation-perfusion scanning, spiral CT or pulmonary angiography.

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