**1.3 Problems with previous cardiac support net therapy (Acorn CorCap, Paracor)**

Devices to prevent cardiac remodeling by physical means, such as covering the ventricles with polyester mesh bags (Acorn CorCap) or shape memory alloy (Paracor), have been developed and used in humans since about 2000 [2–5].

The Acorn CorCap is the most extensively studied of these devices and received CE mark approval in 2001. Randomized clinical trials of 300 cases have been performed in the United States [2, 3, 6, 7]. Although it demonstrated reverse cardiac remodeling, it did not demonstrate prognostic value and was not approved by the FDA. There was a lot of missing data on the primary endpoint (NYHA), and Acorn Cardiovascular, the company developing the device, did not comply with the FDA's request for corrections. On the other hand, the FDA reviewers agreed with the need for this type of device.

The Acorn CorCap wraps the right and left ventricles equally, so applying the necessary pressure (>5 mmHg) to the left ventricle would impair right ventricular dilation and reduce cardiac output (**Figure 1** left panel) [8, 9]. At a contact pressure of 3 mmHg or higher on the ventricle, transmural myocardial pressure (Ptm) decreased in the left ventricle, while no change occurred in the right ventricle. At pressures of 5 mmHg or higher, RVEDP and CVP increased, and mean blood pressure decreased [9]. On the other hand, in the device that pressurized only the left ventricle, there

#### **Figure 1.**

*Comparison between Acorn CorCap and our device. (Left panel) Acorn CorCap has six sizes. The surgeon had to adjust the size to fit. Acorn described that the contact pressure should be 3-5 mmHg. More than 5 mmHg contact pressure on the right ventricular side depresses right ventricular diastolic function. Less than 5 mmHg on the left ventricular side is not sufficient to achieve a meaningful improvement in left ventricular systolic function. (Right panel) iCorNet patient-specific cardiac reshaping net with a hole on the right ventricular side. It is a personalized/prefabricated product that constrains only on the LV side. It can provide sufficient LV wall support (>5 mmHg) without RV constraint.*

was no increase in CVP and no decrease in mean blood pressure [8], even when the pressure on the left ventricle was increased up to 14 mmHg. Pressure-volume area and stroke work, which are indirect measures of oxygen consumption, were significantly reduced, and energy efficiency was improved [8].
